It's hit and miss with VISTA and computers as far as the "unexpected shutdown" problems.
Looking at my reliability information, I show 7 or 8 on 1 420 since November, but only 4 on the second 420. Since Feb of 07, my Toshiba shows 2, one Feb 07, the other yesterday. My E1705 shows 3 in the last year....so who knows. No rhyme or reason, just Windows Recovered from Unexpected Shutdown.
I can't seem to get a consistent reading as to why and when, so troubleshooting is difficult, so I just ignore it.
I figure as long as it recovers, I am ok.
2 XPS 420's, Quad 2.4ghz, 8800GT and 9800GTX, 3gigs RAM (Vista Home)
2 Inspiron 1720's, 2.0 and 2.5 gig processors, 2 and 4 gigs RAM, 8400GM and 8600GT cards (Vista Home and Ultimate)
1 E1705, 2.0 processor, 2 gigs RAM 7900GS. (Vista Home)
2 Mini 9's, Black and Cherry Red......(Windows XP) Love The Mini!!!!!