|mmm There are more than a few reasons why one can gat BSOD (BlueScreeOfDeath)...|
Regardless of the what/why etc.. you likely have files/data on the system you'd like to preserve/safeguard etc.?
Presuming so... get a Linux on CD variant (Knoppix and Ubuntu are the two usual flavours). Boot with that CD; transfer (as in copy ) all data etc. to optical-media and verify they will read/play on at one other system. Then set about resolving your main problem?
Failing drive may cause this (bad sectors); failing RAM - or RAM not securely seated etc...; overheating in the past - check coolng fans (especially the cpu fan)...
Can you get a last known good config to work? Do you have access to Recovery Console?
And if you have an odd-ball OS (is w2k - is XP - is it abird???) who knows what is really going on...? But regardless of that conundrum... one of the above is likely involved?