The current Service Pack level for NT/2k/XP is displayed in the System Properties window, right click My Computer and select Properties to see it. It's usually possible to remove a Service Pack by going into Add/Remove Programs and looking for it in the list. The exception is when a give SP is "slipstreamed" onto the CD, updating the files on the install CD itself so the SP get installed with the OS and you don't have to install it afterward. The only way to go back to a previous SP in this circumstance is to find the original CD on which the slipstreamed copy is based (assuming you have one. If you don't you're SOL). But at any rate, XP SP3 doesn't exist yet, SP2's only supposed to be released sometime early next year.