Why Is My PC So Slow All of Sudden[8 Fixes Included]

It is frustrating to meet PC suddenly slow problem. This guide will explain the reasons why is my PC so slow all of sudden and show you how to solve the issue and speed up the slow Windows 11/10/8/7.


By Hedy / Updated on May 12, 2023

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Scenario: My computer is slow all of a sudden

"My PC was running fine up until last week. All of a sudden I went to turn it on, when it starts up it is too slow and lagging to do anything. I can't even open my settings. Is this a Virus or is there some other problem? Do you guys have any advice for me? Thank you!"


Why is my PC so slow all of sudden?

A slow computer is often caused by multiple factors. Here we list the most possible reasons why is my PC suddenly so slow. If you have the same issue, referring to the following causes may help you solve it better.

✤ Too many programs running simultaneously.
✤ Too many temporary files.
✤ Excessive accumulation of dust.
✤ Windows and drives are not updated.
✤ C drive is full.
✤ Hard drive corrupted or fragmented。
✤ Malware or viruses.

Quick fixes to PC slow all of a sudden

After figuring out why is my PC so slow all of sudden, you can follow the below quick fixes to get rid of PC suddenly slow issue from different aspects.

▶ Way 1. Close background programs

PC getting slower than before is usually caused by too many programs running at the same time, which occupy the processing power of the PC. Even if some applications are shut down, they still continue staying in the background and reducing performance.

To end these background programs, please right-click the taskbar and choose "Task Manager" to open it. Under the Processes tab, you can see which program is biting your memory. Right-click the apps you want to close and select "End task".


▶ Way 2. Run Disk Cleanup

As we mentioned in the reasons why is my PC all of a sudden so slow, low disk space on the system C drive is one of the major causes. Thus, if you find your computer is still running at a low speed, you can clean up your C drive to make it faster.

Disk Cleanup is an integrated tool in Windows that can help you free up space from disks. Type "disk cleanup" in the search box, and select C drive to open Disk Cleanup for C drive window. After ticking the files you do not need and click "OK" to continue.


To deep delete all unnecessary files from your computer, switching to a PC cleaner program is a smart move. It helps you get more space on the hard drive with no effort.

▶ Way 3. Disable startup programs

Startup programs will start automatically every time you boot your PC. If you want to save time on the boot process, it's necessary to disable some unnecessary applications. Just open Task Manager, go to the "Startup" tab and right-click the program that you don't want to load automatically, and then choose "Disable".


▶ Way 4. Check Windows update

If your version of Windows or other software is out of date, you also have the chance to get a slow computer. So check for updates and make sure your computer has the latest Windows and the latest drive. You can press the "Windows + I"  keys to open "Settings" > "Update & Security" > "Windows Update" to take a look.


▶ Way 5. Scan for malware or viruses

If all the above solutions don't work, your computer may be infected by malware or viruses. If you don't have good anti-virus software installed, you can try Windows built-in Defender to run a clear scan.

Do the following: press "Windows + I" to open "Settings" > "Update & Security" > "Windows Security" > "Open Windows Security" > "Virus & threat protection" > "Scan options". Select "Microsoft Defender Offline scan", and then click "Scan now".


After your PC restart, check whether it runs faster than before. If not, keep reading.

Advanced fixes to PC slow all of a sudden

Since various factors lead to a sudden sluggish PC, you may need advanced help when the quick fixes fail to solve the computer running slow issue. In this part, you will use a reputable disk manager called AOMEI Partition Assistant Professional which is compatible with almost all versions of Windows 11/10/8/7.

It can solve many tricky disk and hard drive problems like cloned SSD won't boot Windows 10, extending volume greyed out, etc. So, the PC gets slow all of a sudden issue can be fixed easily and effectively.

Below, we will mainly talk about three methods you can apply to solve the slow issue and speed up your Windows computer. First of all, download the demo version to have a try:

Download Pro DemoWin 11/10/8.1/8/7/XP
Secure Download

▶ Way 1. Add space to system C drive

If your system partition is nearly full, your computer certainly gets slower than usual. In such a case, you can increase the size of C drive. Apart from moving folders/programs to another drive or deleting large files on C drive, AOMEI software provides you with a practical function to directly extend the system partition.

Step 1. Install and open AOMEI Partition Assistant Professional, right-click drive D (or other partition with enough space), and select "Allocate Free Space".


Step 2. Set the size you want to move to C drive, then click "OK".


Step 3. Click "Apply" to commit the whole operation.


▶ Way 2. Schedule defrag partition on your HDD

Too many fragmentations can cause slow PC performance. Thus, it's not a bad idea to defrag your HDD partition to make your computer run faster and scheduling defrag partition can keep your HDD always in a good state.

Warning: Never defrag your SSD. If your hard drive is an SSD, turn to making 4K SSD alignment.

Step 1. Launch AOMEI Partition Assistant Professional, select the target disk or partition, and choose "Disk Defrag" or "Advanced" > "Defrag Partition".


Step 2. In the pop window, you can see all your used drives. Because we need to set a schedule, you need to click the button "Schedule", but you can also directly defrag the disk or partition if you want.


Step 3. In the schedule settings, you can select drives, the specific date and time to defrag the target drives, then click "OK" to save the settings.


Step 4. Click "Conditions", you can set the rate of fragmentation to trigger the schedule to defrag your disk and tick other options to help you make a detailed schedule based on your needs. Then click "OK" to save the settings.


▶ Way 3. Upgrade HDD to SSD

It’s known to all that SSD has more advanced benefits than HDD, so it's warmly recommended to upgrade your current HDD to SSD. AOMEI software will help you realize the SSD upgradation without reinstalling the OS and without rebooting during the process.

Note: If you are working on SSD right now, why not clone smaller SSD to larger SSD to get better system performance? If you don't want to clone the entire hard drive, you can choose to migrate only OS to SSD.

Step 1. Connect the destination disk to your PC, and run this disk cloning software. Click "Clone" > "Clone Disk".


Step 2. In the pop-up window, choose "Clone Disk Quickly" and click "Next". When you intend to clone hard drive with all sectors, choose "Sector-by-Sector Clone".


Step 3. Select your previous HDD or the smaller SSD as the source disk. Click on "Next" button.


Step 4. Select the new SSD as the destination disk. Select "Optimize the performance of SSD" to make SSD partition alignment. Then, click "Next".


Step 5. Here you are allowed to adjust the partition size on the target disk. Then, click "Next".


Step 6. Then you will receive a note about operating system boot. Keep it in mind and click "Finish".


Step 7. Here you can preview the operation result, click "Apply">"Proceed" to implement the operation.


After cloning, remember to change the boot order so that you can boot from the destination SSD. Then, you won't say "my computer is slow all of a sudden" because you have gotten a faster system.

Final verdict

Thanks to this passage, you not only know the answer to why is my PC so slow all of sudden but also get several useful solutions to it. As you can see from this post, a slow computer is caused by various reasons and can be fixed by many solutions. Among all the fixes, quick fixes are recommended. They are easy and effective and can save you from a sluggish computer quickly.

By the way, if your computer is running slow on the Windows Server system, you can turn to AOMEI Partition Assistant Server Edition.

Hedy · Staff Editor
Hedy is an editor of AOMEI Technology. She is very good at solving problems of partition management, and she wants to share all the problems she had already solved to users who met the same questions.