Did you try to boot in safe mode and use system restore?
If it's a system from a big manufacturer (Dell, HP, Acer, Asus, etc...) there's a hidden recovery partition on the hard drive. Check your system manual to know which key to press to boot on it. The recovery partition is the same as a recovery cd.
If everything else fails, then you can contact your system manufacturer and ask for a recovery cd, but most of them will charge you for that I think.