Prime95 - is a small and easy to use application that allows you to find Mersenne Prime numbers designed for overclockers. Mersenne numbers can be proved composite (not prime) by either finding a factor or by running a Lucas-Lehmer primality test.
Prime numbers have long fascinated amateur and professional mathematicians. An integer greater than one is called a prime number if its only divisors are one and itself. The first prime numbers are 2, 3, 5, 7, 11, etc. For example, the number 10 is not prime because it is divisible by 2 and 5.
A Mersenne prime is a prime of the form 2P-1. The first Mersenne primes are 3, 7, 31, 127, etc. There are only 40 known Mersenne primes.
There are two ways to use this program. The automatic way uses a central server, which we call the PrimeNet server, to get work to do and report your results. Anyone with Internet access, including AOL, CompuServe, and dial-up ISP users should use this method. You do not need a permanent connection to the Internet.
The second method is the manual method. It requires a little more work and monitoring. Recommended for computers with no Internet access or with some kind of firewall problem that prevents the automatic method from working.
Download: 
Prime95 30.19 Build 20.zip - 8.4 MB