This could be caused by several things:
Programs running in the background
A scan that is running such as a virus scan
Updates running (for Windows or your anti-virus program, etc)
A large number of temporary files
First, look at the information in our tutorial
Slow Computer Checklisthttp://www.bleepingcomputer.com/forums/t/44690/slow-computer/
Second, examine the programs that start when Windows starts and eliminate those that aren't necessary to run until you want to use them.
Removing them from the startup menu does not stop them from being able to be opened as you need them but be careful not to disable your snti-virus application, firewall, anti-malware programs that give realtime protection and essential Windows services.
Use Startup Inspector, which is superior to using the Microsoft utility msconfig to regulate your start menu as it shows you for the most part what each entry is, its name and the ap it is connected with and lessens the chance of stopping one that may be important to keep running at all times.(like an av program or firewall)http://www.windowsstartup.com/
Third: Schedule anti-virus scans to run at a time when you will not likely be using the computer.
I also suggest that you take advantage of the Windows One Care Free Scan from Microsoft, an on-line scan that will Check for and remove viruses, Get rid of junk on your hard disk, and Improve your PC's performance.
Go to Windows Live Onecare Free Scan
It will say "Get a free PC safety scan"http://safety.live.com/site/en-us/default.htm
Make sure you click "Full Service Scan"
in the middle of the page and not the "Try It Now Free" on the right side.
Allow it to download an Active X component.
Choose "Complete Scan" in the window that opens
Do not click on anything else that offers you a free trial or to sign up if you live in the US.
Allow it to scan - it may take quite, maybe two hours or so depending on how big your hard drive is and how fragmented your registry and drive are.
Edited by Enthusiast, 05 October 2006 - 03:56 PM.