The problem of installing SP2 and then not being able to find Movie Maker appears quite often in the newsgroups.
First check which version you do have - it may already be updated and you didn't realise. Check here for how to do that.
Movie Maker is generally found at;
Try clicking on;
type in - moviemk.exe
If you can't find it, or it doesn't open properly, then there are easy to follow instructions given by Dean Rowe, for the manual re-installation of the Movie Maker system files, in his WebLog. Rather than reiterating what has been so well written already, I will give you a link to the information. Remember if you find you cannot follow it, you can always contact me using the link to the left and ask for help.
Also look at your spyware removal tools. Some have been known to remove useful files from programmes.