Server crashes inexplicably

I have a 4-year old Win2000 server Dell PowerEdge 4400 RAID 5 (8 60GB hard drives with 39GB free space) with 2 1000mhz Intel Pentium III, 768 MB installed memory that crashes (black screen, no BSOD, server is on but no keyboard or mouse response and comes back up no problem when turned off and back on) or reboots itself about every 2 weeks, usually when little to no traffic, rarely in heavy traffic times. Nothing ever in any Event log for hours or days prior. This has been happening since I took over the server a year ago. Sometimes I get a mini dump but I can’t read or interpret them as I am not trained. Uses Active Directory. This is an internal LAN, no Internet connections, no viruses. As I am not trained, I don’t know what to check or where to go with this. I’ve posted to other tech forums but get no responses. Please help!