Nothing works after uninstalling ie8!

Hello,

i uninstalled ie8, because i thought to reinstall it using firefox (it was very slow and had many errors). after unintalling, most of the programs on my computer don't work, it says that i "might not have permission to access" it. i cant open firefox, not windows restore or other apps, almost nothing!, except microsoft office. do anyone have an idea?

thank u very much for helping
i really don't know what to do except of reinstalling windows xp.