Prime95 is a Windows program written that searches for new Mersenne Prime Numbers. This extremely demanding application make a great utility to "stress test" a computer to ensure stability under a heavy load. Prime95 is free to use. The Electronic Frontier Foundation is offering a $100,000 award to the first person who discovers a ten million digit prime number, and restrictions on the award do apply to users of Prime95. Read about the restrictions here.
CPU-Z is a freeware program that gathers information on the integral hardware of your system. It will identify information about your processor, (including name, number, voltage, clocks and cache information), motherboard (model, revision, BIOS version, chipset), memory (frequency and timings) and operating system. CPU-Z is a very useful diagnostic tool for anyone using an x86-based computer.
Ultimate Boot CD[Download Link]
The Ultimate Boot CD is a disk filled with useful diagnostic tools. It can run floppy-based diagnostic tools from CDROM drives. A wide variety of testing utilities are consolidated onto this disk, making it a useful tool for end users and technicians to troubleshoot and test hardware.
MS Security Essentials[Download Link]
Microsoft Security Essentials is a free anti-virus solution, available for download from Microsoft. MSE is known to be easy to use, has low system overhead, and is constantly updated with new virus definitions. Every computer should have some sort of Virus protection. If yours is unprotected, we recommend installing Microsoft Security Essentials.
Spybot S&D[Download Link]
Spybot detects and removes spyware, which silently tracks your surfing behavior to create a marketing profile for you that is transmitted without your knowledge and sold to advertising companies. If you see new toolbars in your Internet Explorer that you haven't intentionally installed, if your browser crashes inexplicably, or if your home page has been "hijacked" (or changed without your knowledge), your computer is most probably infected with spyware. Spybot-S&D is free, so there's no harm giving it a try to see if something has invaded your computer.
Ad-Aware is a free anti-spyware program, designed to prevent, remove and repair damage caused by Trojans, Worms, Spyware and other malicious programs. A program like Ad-Aware is your first line of defense in preventing malicious software from damaging your computer.