The E5200 family of CPU's is based on the Wolfdale core. They have a relatively low FSB freq (200 MHz) and relatively high internal multipliers (starting at X 12.5). That combination means that they tend to overclock like banshees.
Very important - what motherboard?
And if your motherboard has a locked BIOS (no user access to BIOS settings), you may not be able to overclock your CPU.