Frequent Hangs, Shut offs, Dumpings

I have workstationg with the configuration of PIII-650, Memory 192 MB, HDD 10GB. Everything seems to work fine when the CPU cabinet cover kept open but often it hangs, starts memory dumping or shuts of after a while cabinet cover replaced back. I tried chaning the SMPS, reinstalling NT (almost few times) though these actions did not solve my problem. Any help in this regard from the hitech guy is appreciated.

Thanx in advance….
ravi