If you have Windows Vista… and it boots slow… and you have a multiple core CPU… read on. You can speed up the booting process by doing the following: “Run msconfig (type it into the Start search bar, press enter). Click boot, then advanced options. Then change the number of processors to 2 or 4 (or 8 if you’re really awesome), and Vista will use all of ’em when booting, not just a single lonesome core.”
Detailed instructions and pictures here.