I am contemplating building a new PC with Windows Vista. The case I am looking at has a 500W power supply. It has a 20-pin mobo connector alongside an additional 4-pin mobo connector. Can this set up be used with a mobo that has a 24-pin connector? Thanks.

Yes. Most PSU's are coming with a SPLIT connector so it will work with both kinds of boards.

If you buy a case that is sold with a PSU already installed, there is a higher probability that the PSU is sub-par. I suggest you source your case independently from the PSU & possibly buy the case locally. The only kicker to that is, a local purchase excludes you from many of the rebate deals on the internet. For instance, Fry's Outpost just sold out on their Antec -- Solo; P180 & Nine Hundred towers, but the rebate deal will probably be back again before long. As we all know, PC' are getting power hungrier these days & you pretty much get what you pay for with PSUs. Buy one that's dependable & you won't have much to worry about for a long time, do otherwise & you're pretty much going to regret it. I recommend something literally *heavy* with adequate Wattage & Amp distribution on the 12V rail, Active PFC enabled, 24 or 20+4 pin connector & one that's compatible with the newest ATX standard (12V v2.3) or at least 12V v2.2 compliant. If you have a 24-pin motherboard, you might as well get a 24-pin PSU & be done with it.