Routinely doing maintenance on the computers in your household is probably the most overlooked but simple and inexpensive way to wring out additional speed from your computer and your high-speed Internet connection. Follow these simple maintenance steps below and you should immediately notice a difference when you browse the web or open a program on your computer.

Free up disk space.
By freeing up disk space, you can improve the performance of your computer. The Windows Disk Cleanup tool helps you free up space on your hard disk. The utility identifies files that can safely be deleted and then enables you choose whether you want to delete some or all of the identified files.

Use Disk Cleanup to:

Remove temporary Internet files and Internet history: Each of your web browsers cache or store a copy of each page you visit for faster access later. Therefore, removing these files from time to time will increase speed. In Internet Explorer, hit the Tools menus, Internet Options. On the General Tab, you'll see a History area. Click the Clear History button.

Remove downloaded program files

Delete old, unwanted files and empty the recycle bin: After going through your saved files and deleting the ones that are old or unwanted, simply go to the recycle bin and under the tasks, click Empty Recycle Bin.

Remove Windows temporary files

Remove optional Windows components that you don’t use

Remove installed programs no longer in use

To use Disk Cleanup:
1. Click Start, point to All Programs, point to Accessories, point to System Tools and then click Disk Cleanup.
2. In the Disk Cleanup for dialog box, scroll through the content of the Files to delete list. Choose the files you want to delete. Clear the check boxes for files that you don't want to delete, and then click OK. When prompted to confirm that you want to delete, click Yes. After a few minutes, the process completes and the Disk Cleanup dialog box closes.

Scan for and remove Spyware
Spyware collects personal information without letting you know and without asking for permission. From the Web sites you visit to the usernames and passwords, spyware can put you and your confidential information at risk. In addition to privacy concerns, spyware can inhibit your computer's performance.

To combat spyware, consider using AVG Anti-Virus or other anti-spyware software.

Download AVG Anti-Virus for free at http://free.avg.com .

Download AdAware for free at http://www.lavasoft.com/single/trialpay.php

Routinely defragment the computer
Disk fragmentation slows the overall performance of your system. When files are saved to you internal hard drive, your computer breaks it up into smaller pieces and stores them wherever space is available on your hard drive. Over time, files and programs can become so fragmented that it will slow your computer because it must search the hard disk when a file or program is opened to piece it back together. Disk Defragmenter is a Windows utility that consolidates the fragmented files and folder so that each occupies a single space on the disk. With your files stored neatly, reading and writing files to and from the disk speeds up. Regularly defragmenting - preferably monthly - is optimal for superior performance.

To use Disk Defragmentor:
1. Click Start, point to All Programs, point to Accessories, point to Systems Tools, and then click Disk Defragmenter.
2. In the Disk Defragmentor dialog box, click the drives that you want to defragment, then click Analyze. After the disk is analyzed, a dialog box will appear letting you know whether to defragment the drive. To defragment the selected drives(s), click the Defragment button.

Source: http://www.microsoft.com/atwork/getstarted/speed.mspx