Alpha Client is freezing and crashing on Launch

So I am on Windows Vista and I have been trying to get LoL to launch for awhile, but it seems like I was forced into the Alpha Client when I didn't want it. Now when I try to launch, it freezes. The Alpha client is just showing as black. I can't even get the option that allows me to switch to the Legacy Client. I have tried to remove the program from my computer, but it just isn't happening. I can't figure out what to do. Any ideas on how to get on this or how to get rid of this Alpha client and get the Legacy client back?