
Using a computer over time without protection from Spyware and Adware and Malware will cause it to run slow. A typical PC does not have any software to protect it against the Spyware, Adware and Malware that slow PC's down to a crawl.
Here are a few things you can do to fix the slow computer problems.

Temporary File Cleanup can be done through Disk Cleanup. This is located in the System Tools section of Microsoft Windows. Click start, programs, Accessories, System Tools, Disk Cleanup. Check off Temporary Internet Files, Recycle Bin, Temporary Files, WebClient.Publisher Temporary Files and Setup Log Files. Do not check Compress old files.
Click OK, then Yes.

Delete Internet Browsing History
Even though you have used the Disk Cleanup Utility to cleanup Temporary Internet Files, do another cleanup through your browser. In Internet Explorer, use the Tools Menu.
Click Tools, Internet Options. On the General Tab, click Delete...
Check off all the boxes - if you maintain your user ID in websites you visit, do not check off cookies, you can clean that manually later.
Click Delete. If you would like the browser to clean it on every exit, check off the box marked Delete browsing history on exit.
For Firefox:
Click Tools, options, go to the section marked Privacy. Click on the link "clear your recent history" and select from the drop down box how much history you want to delete.
To clear cookies, click the "remove individual cookies link" and select the cookies you want removed. Remove everything you do not recognize as a familiar website. You can also click on Remove all Cookies if you want all of them removed.
For Safari:
Click on Edit, empty cache.
Click on History, Clear history, clear.
To clear everything and reset Safari, choose Edit Reset Safari and select the areas you want reset. Click Reset.
Cookies
Manual cookies cleanup can be done in Internet Explorer by selecting Settings, View Files.
You can also Use: Start Run, and type cookies in the box to bring up all of the cookies on your machine. Highlight and delete the ones you do not want.
Spyware removal
Use a good Spyware scan and removal tool such as Spyware Terminator (Free)
Malware Removal
Use a good Malware Removal tool such as Malwarebytes
Trojan removal
Use Trojan remover. This program can be used for 30 days free.
Defragment your Drive
Click Start then run. Type Defrag.
The dialog box that appears will show a list of your hard drives.
Choose Local Disk C:
Click Defragment.
Do not run anything else while this is running. The system is going to be moving files and those files need to be closed for the defragmentation to be completed..jpg)
Check Disk Space
Right click on the My Computer Icon on the desktop.
Select Explore. Right click on the Local Disk (C:)
Select Properties. The graph displayed will tell you how much free drive space you have. If you have less than 15% free, your system is too full to function well.