Just before you perform any cleaning steps with the Windows operating system it is good to make sure that you have a healthy computer system. This can be done by testing the computer’s RAM and hard disk. Without this, if you try to perform any of the following steps, it is possible that you might harm your computer more than doing any good.
 
There is a good software application called Memtest to test RAM. The hard disk surface can be tested with UBCD4WIN.
The first place you have to go to is in the Windows directory, called as the Temp folder. This contains the data the computer stored during software installation. But if you want, it can be deleted completely. So, we can go there and delete all the files present in this folder. The computer will ask you if you want to delete particular files which are hidden or system files. You mustn’t delete just these files; delete everything else.

 

For the next place we shall visit, you will need to see all your hidden or system files. To do this, just go to My Computer -> Tools -> Folder Options. On this, click on the View tab and click the radio button that says “Show hidden files and folders”.

Then, we go to C: -> Documents and Settings -> Administrator -> Local Settings -> Temp. You will find a lot of folders here with alphanumeric names. All this content can be safely deleted. However, if you are sceptical about any file, you might choose not to completely delete the file but just move it to the Recycle Bin. Then restart your computer. If your computer starts well, then the files were unnecessary and you can empty your Recycle Bin completely. You may not do this immediately if you choose not do. Wait for some time, operate your computer as you normally do and if no problem occurs, then go ahead and peacefully empty your Recycle Bin.
We move on to the Internet Explorer next. Here you will find a cache space that is used to store web content for easy and fast access. We go to Tools -> Internet Options. In the General tab, you will find Temporary Internet Files. Click on the Delete Files button. Mark ‘Delete All Offline Content’ and click on OK. You can also delete cookies if you want.

 
In the Mozilla Firefox browser, go to Tools -> Options -> Advanced -> Network.  You will find Offline Storage. Click the Clear Now button.

All steps mentioned above can be done automatically by using a special software application. Here, we will use CCleaner. It can be downloaded from here. When you start CCleaner, you will see a screen like this.

Just before you start to do any cleaning, it is recommended to perform some preparation steps. First, uncheck Empty Recycle Bin. Then, go to Applications if you use the Firefox browser and uncheck Internet History. If you are using the Opera browser, then uncheck Internet History there.
Click on Analyze. It will show what content can be deleted. Then click on Run Cleaner.
To clear Windows XP registry, click on the Registry tab. Click on Scan for Issues. Then click on Fix Selected Issues.

CCleaner will then ask “Do you want to backup changes to registry?” Click on Yes.
Cleans the following:
Internet Explorer
Temporary files, history, cookies, Autocomplete form history, index.dat.
Firefox
Temporary files, history, cookies, download history, form history.
Google Chrome
Temporary files, history, cookies, download history, form history.
Opera
Temporary files, history, cookies.
Safari
Temporary files, history, cookies, form history.
Windows
Recycle Bin, Recent Documents, Temporary files and Log files.
Registry cleaner
Advanced features to remove unused and old entries, including File Extensions, ActiveX Controls, ClassIDs, ProgIDs, Uninstallers, Shared DLLs, Fonts, Help Files, Application Paths, Icons, Invalid Shortcuts and more... also comes with a comprehensive backup feature.
Third-party applications
Removes temp files and recent file lists (MRUs) from many apps including Media Player, eMule, Kazaa, Google Toolbar, Netscape, Microsoft Office, Nero, Adobe Acrobat, WinRAR, WinAce, WinZip and many more...
100% Spyware FREE
This software does NOT contain any Spyware, Adware or Viruses.
CCleaner also can be reached online http://www.ccleaner.com/  or on CNET http://download.cnet.com/ccleaner/