Had to get a Windows XP Pro install down to as small as possible to deal with a small hard drive. The smallest footprint I could get it down to (without going to heroic lengths) was 3.6GB. This includes all Windows updates through today 3/25/08. I turned off system restore. Removed all unneeded Windows programs, and removed the update temp files. Basically the only thing usable is Internet Explorer 7.
I realize Microsoft’s goal is not efficiency, but compared to Knoppix Linux at less than 650 MB and DSL (Damn Small Linux) at 50 MB; What’s all the bloat?