OS X completely.
If you have an OS X installation DVD, boot from it and go from there.
Make sure that you backup everything that you still want. Movies, pictures, music, documents, etc.
You already back your stuff up, right?
P
Can someone help me with this problem? Several weeks ago I updated Safari for Snow Leopard from CNET Tracker but what downloaded was Safari for Lion. I posted the situation on the forum and was advised on what to do. I solved the problem by downloading mac osx combo 10.6.8. However, ever since, my mac has gone nuts. I also noticed that parts of the browser were missing. Then Safari started lagging, freezing, and crashing several times a day. I tried to trash it and then download it again but now in does not want to download completely. It stopped downloading this morning after several hours. I re-downloaded it starting at 11:30 am. It's been stuck at 68% since 4pm and will not budge. Can someone give me a clue as to how I can fix this problem.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic