You can raise it through BIOS or you can download a program, although at the moment I forgot what it was called. Then get CPU-Z to see what your clock speed is.
I have this "celeron d" overclocked to stock @3.6(18*200fsb) easy 1.2 gig overclock.
Clockgen works great for finding max clock without having to reboot into bios every 5mhz. Test with superPi for stability. My max was @4.3 w/hs xp120 and small bump in voltage on msi neo2 865PE.