Okay saving your music you should have or buy an external harddrive, in this day and age it is always good to have one anyway. There are alot of reasons why vista might freeze.

Your computer mightnt have enough ram.
you might have enough to run vista but you might have other resource intensive programs which are chugging it up.

You might be running antivirus like mcafee which is a resource hog (if you do uninstall and get the free avg)
you might have a virus (inthat case refer to avg)
you might be riddled with spyware (download spybot search and destroy)

i would turn off things like windows sidebar and things

in summary i couldnt really tell you the exact cause without snooping through your computer, if the problem persists you might have to reinstall with the disc (fairly straight forward)

http://free.avg.com/download-avg-anti-virus-free-edition better less resource hog anti virus

http://www.safer-networking.org/en/download/index.html free and brilliant anti spyware, run a scan just to be sure

also a registry clean will perk it up regardless

http://www.filehippo.com/download_ccleaner/

all free and really good products, use them and try the above mentioned possibilities and then come back and update your post if the problem persists