XPS 700 Crashes and Freezes for no apparent reason

My comp's been freezing and/or crashing a lot lately.  Ir won't just do it while doing anything specific, it just dumps.  I've run the driver diagnostics,  registry diagnostics and cleaner, and several complete virus scans, but they don't bring up anything.  I suspect it's a driver issue, but I'm not certain.  Anything you guys can suggest to help?