I think I messed my computer up big time can someone help me?

[HoneyBrisk]

So I bought a kaspersky virus protection and had to uninstall my McAfee. The problem was I couldn't get McAfee to uninstall. So I went on some site that said go to my start on my computer, then run and put in regedit. Then it said export files and then try to delete the Mcafee file I tried it and of course it didn't work. Then I found a link to a McAfee uninstaller that I only wish I saw before messing with the registry. Now my computer is acting weird I'm clicking on files that won't come up and now my internet isn't working and I know nothings wrong because I'm on my laptop right now using the internet. So my question is how can I get my computer back the way it was??