Well mate I can't see how anyone can help you without knowing exactly what it is you changed.

Anyway if all else fails then reloading the game should fix it, unless you backed up the files before editing them in which case you will just have to chaneg back the files.

You should always back up, for the terrible god Murphy is displeased with those who fail to back up and so he inevitably smites them down with errors and crashes to desktops.