Go to Start (Is it still actually called that officially in Vista, since it's now just a logo), right click on Computer, and select Properties. For me, I see at the top a section called Windows edition, and mine says
Windows Vista Business
Service Pack 1

While SP1 is not a miracle cure all for Vista (just got done reseating network cables and trading ports to see why mine was dropping 80% of the packets to the network), it is slightly better and worth getting. If you don't have it, go to Start, and type in Windows Update. I don't think SP1 is going out over automatic updates yet, but it will show as a choice if you run the updater manually.

Click on START MENU or whatever the heck they're calling it these days.

Windows Update will recognize PCs with known problematic drivers and postpone downloading Windows Vista SP1 until the PC has updated drivers or other applicable updates.

This from a guy who actually works for MS. <headslap>

Sisyphus

It's a little scary just how deeply I wandered into Wikipedia's Greek Mythology section after looking up this character. I knew I had to Alt-F4 when I wound up at Amsterdam's Vrolik museum site looking at a baby cyclops.