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# Remove Spyware and Viruses* Spyware and viruses are a leading cause of computer slowing. See this article to learn how to remove them.
* Update and run your spyware and virus software at least weekly.
* If you do not have tools installed to protect against malware, spyware, and viruses, download a free copy of AVG Anti-Virus 8.0 (free for personal use). Also, Microsoft's Windows Defender is a widely-used anti-spyware tool that is currently distributed freely for users with a "Genuine" copy of Windows. Windows Defender is also included with other Microsoft services and products such as Live OneCare and Vista.
* Download and install Mozilla Firefox from http://www.mozilla.com. It will allow you to import all of your Internet Explorer settings, and is much less prone to malware than Microsoft Internet Explorer. It will prompt you with a "Set as Default Browser" message. Check "Don't show this again" and click "Yes".
* If you have a particularly difficult infection, try using the Quick Virus Remover. It is a free utility that is not a replacement for commercial products, but can be helpful for removing some of the most common viruses.
# Defragment Your Computer - This will place similar files physically closer on the hard disk to improve load speeds.
* Click start, again, then click run.
* Type, "dfrg.msc" in the text field.
* Click Defrag to start it.
# Remove unwanted software.
* Click start, then click control panel.
* Click add/remove programs.
* Highlight any old software you do not use and then click "remove".
# Stop unwanted Start-Up programs.
* Run msconfig
* Choose startup box
* Select uncheck programs you don't want to run on startup
*
OR
* Click Hereand download StartUpCPL.
* Install the software you have just downloaded.
* Open control panel, select Start up.
* Disable any programs you do not want load automatically
* Disable Services you do not use or need. Open control panel, open Administrative Tools, and select Services. Disabling the wrong Services may lead to serious problems that you may not notice right away. Please consult a reference such as overclockersclub.comfor information on specific Windows XP Services.
# Make Windows load faster
* Click Start, then Run.
* Type in 'msconfig' and press enter.
* Click on the BOOT.INI tab at the top.
* Over to the right there will be a box labeled Timeout with 30 in it. Change the 30 to a 3.
# Speed Up Processing Time
* Turning off the fancy Windows XP graphics will noticeably increase the speed of your computer.
* Go to Start, (Settings), Control Panel, System. NOTE: You may need to 'Switch to Classic Mode' to see the System applet.
* Go to the Advanced tab. Click the Settings button under Performance.
* Select the 'Adjust for best performance' radio button, then Apply, and OK.
* The graphics aren't as flashy, but your computer will run a lot faster.
source : http://www.wikihow.com