Whoops! broken registry

Hullo

I have windows XP, service pack 2 fully installed, along with all windows updates and windows firewall and my pc has been working perfectly for a long time.

Recently I did something, not sure what it was

But now when I right click on anything (ie my computer, or a file within my computer) a window pops up saying

"bad language directory" at the top then

"The base UI directory is invalid" I then click ok and i get the following message

"Hkey/corel4/config something something is no longer avaliable" (the message has gone acctaully so I cant remember exactley but its something to do with a registry key and corel 4 (which is unistalled))

I then click ok, and the first error message appears, then the second, then the first again. Then it all works fine

Additionally, and rather more annoyingly, 90% of applications I try to run now crash before they start I get a pop up window saying

"blah blah has encountered a problem and needs to close we are sorry for the inconvenience"

Also the installers for the programs have stopped working IE, Team speak crashs when I start it. So does the Team speak installer. HOWEVER if I re-download Team Speak and Reinstall it then works FINE.

So obvisouly something has messed up with registry or something

I can of course just reinstall everything but that takes a lot of time, just wondered if anyone had any words of wisdom/advice (I'm not reformating!)

thx a lot =0