Vista 64 bit, I bought it with a free coupon for Windows 7, but I forgot I had it and the deadline passed for me to redeem it. *sigh*. I have Windows Vista 64 bit Business Edition (Which is supposed to be much better than Home edition. For those looking at Vista, I am told that Home edition is the source of most of Vista's problems). Once I upgraded to the latest service pack, I haven't had any problems, the system works like a charm. My only complaint however, is the account user control, which is nice when it comes to security, but is really annoying and gets in the way of just about EVERYTHING. What's funny is that windows has always had user account control, but only in Vista has it become this intrusive. I haven't disabled it yet. But actually the thing that REALLY bugs me, is Vista's default setting of organizing folders. If you have like, more than 3 songs in a folder, it will automatically change the organization tabs to "Genre", "Star rating", "Artist", "Length". This is quite frustrating since I use iTunes and don't do any music organizing using Windows Explorer. I prefer to just use organize by "Name", "Type", and "Date Modified" for everything.