Sure. You can download the QFECheck tool from MS (Google it) which scans the registry and will list the installed hotfixes. I've seen other similar tools which do similar things, also probably a Google search away. Otherwise, you should be able to see them in Add/Remove Programs. Assuming you're using XP SP2, open Add/Remove Programs and check the "Show Updates" checkbox at the top of the window. If you scroll down, you'll see a list of them.