|The video card is an old, low end TurboCache card, there's no point overclocking it. If you're unhappy with the graphics performance, get a new card.|
It would help to know which DDR2 RAM you have- 533MHz, 667MHz, 800MHz, etc. Depending on which you have, it can limit the overclocking options. For the following overclock suggestions, I'm going to assume you at least have DDR2-667. Two things to keep in mind when overclocking an LGA775 system is the faster the FSB, the better the performance, & you should always strive for a CPU:DRAM frequency ratio of either 1:1 or 1:2.
The default settings for the E5200 are 12.5 x 200MHz @ 800MHz FSB. Your board supports up to 1333MHz FSB. Since the E5200 overclocks quite well, you should have no problem running it at 3.0GHz (9 x 333MHz) @ 1333MHz. The RAM frequency should be 333MHz (667MHz DDR) to run in sync at 1:1. If you have DDR2-800, it should be underclocked to DDR2-667 speed. A 1:2 ratio is not possible.
Being able to overclock will depend on whether your BIOS has all the required options or not. Here's a generic list:
CPU frequency = 333MHz
CPU multiplier = 9.0x
RAM frequency = 333MHz (667MHz DDR)
CPU:DRAM ratio = 1:1
PCIe frequency = 100MHz
Spread Spectrum = disabled
SpeedStep = disabled
EDIT: I didn't look at the manual but if you have the 2.66 memory multiplier as mentioned by kuwese & don't have the option to set it to 2.0, your overclock options will be very limited.