its a customs built pc. has the m7ncd mobo with 1gb of mem winxp pro sp2 .. when the pc is being used it just shuts off and does a 2 tone beep.. high pitch then low pitch and just sits there. i suspect bad mobo or processor but dont have another one to try rigth now. sometimes the pc will last 30 min sometimes 4 min even once it lasted a day before shutting off. it doesnt matter what type of app im runnin still crashes. any ideas of things i could try without going to the new mobo/cpu would be greatly apprecietated. thanks

have you tried seeing the power dc output in bios, see if the dc output is fluctuated so much. if so then you need an ups to stabilize your electricity...
otherwise you look up for the incompatibility among components (because it is custom built) you basically can see it on the manual book or your hardware manufacturer website.
and look also when the pc crash, is it while you play certain software, or when the cpu shoot up to 100% for a range of time or when the ram is in small amount, etc.

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