[NTLUG:Discuss] one more OT question my laptop please

[Fred James]

All
Gateway MX8734; MS Vista Home Premium - planned to upgrade to XP Pro SP2 
as a dual boot with Linux (Mandriva 2008 or something like that)
Box has been back for warranty work twice
    once because it powered off and wouldn't power back on
    once because hung (mouse and keyboard had no effect) and then timed 
out (blank screen - although it was still powered on, it wouldn't un-hang)
Now it powers off after several (exact quantity not known as yet) hours 
idle - I have been leaving it idle as a test to see if Gateway had fixed 
the problem, before I move on to the plan noted above.
(more detail upon request)

Question:  Is this more likely to be a Gateway issue, or a Vista issue?

Thank you in advance for any help you may be able to offer
Regards
Fred James

PS:  The power off occurs whether user is logged in or not