Server crashes

The Chelmsford server has been crashing randomly, about every 3-4 days, from the first day it was installed (2-3 years now). I have tried lots of different things but it seems quite random. I tried Memtest86 which is used to check the RAM. The instructions say that if the test itself crashes the problem must be more serious (motherboard or processor related). The test did indeed crash in my case at 57% hence the need to get a new server. The worst problem is keeping confidence in data security from the staff.