Use the following web sites at your own risk.
Tutorials And Guides
These web sites have useful Tutorials about Processors, Motherboards, Memory, Video Cards, Monitors, Hard Drives, Floppy Drives, BIOS etc.
http://www.pcmech.com
http://www.hardwarecentral.com/hardwarecentral/tutorials/
http://www.pctechguide.com/
http://www.tomshardware.com/
http://www.compguystechweb.com (Thanks to bobthebuilder for the link)
http://pcsupport.about.com/ (Thanks to bobthebuilder for the link)
FAQ's and Tips for computer problems (Thanks to michaelangelo777 for the link)
http://www.computerproblems.com/
A useful site for WindowsXP users (Thanks to Bobhome for the link)
http://www.xp-erience.org/guides.php
Another useful site for Windows users. Click on Tips And Tricks link at the top of page. (Thanks to Bobhome for the link)
http://www.onecomputerguy.com/
The web site has information about PC Power Supplies. Also there is a table on this page, which shows how many Watts each hardware component uses. (Thanks to Scottyj72 for the link)
http://www.howstuffworks.com/power-supply3.htm
Also check out this link from the above web site, which has useful information about computer hardware and software.
http://www.howstuffworks.com/category.htm?cat=Comp
"The Windows Registry Guide, formerly Regedit.com, provides an extensive range of registry tweaks, tricks & hacks for optimizing, enhancing and securing the Windows operating system." (Thanks to Bobhome for the link)
http://www.winguides.com/registry/
"The Windows Guide Network provides technical resources and support for tweaking, managing and securing the Windows operating system using the registry, scripting and security."
http://www.winguides.com/
This site has lots of information about BootDisks, PC Support and Essential Utilities
http://www.bootdisk.com/