lost windows

I recently ran an anti-virus program on my cmputer, and
then restarted like it said to. When I restarted my
computer Windows did not load! arrggghh! I have tried
everything to get it back but I never recieved a windows
xp disc with my computer. Have recently rang for a
recovery disc but no luck there either as it hasnt
arrived! Wen i try and run system restore it says it
can't find %systemroot%\system32\restore\rstrui.exe
Don't know wot i am supposed to do know and haven't had
any luck on the site wandered if anyone can help me,
hoping my computer isn't doomed!!!