You said Athlon 64x2 7750 BE, the important thing there being the "BE", which means black edition.
CPUs derive their clock speed from an initial bus speed and a multipler, so an E5200 for example has a multipler of 12.5 and runs off a 200Mhz initial bus speed, making it run at 2.5Ghz.
Normally this multipler is locked, so that to overclock you have to edit the bus speed. This has a side effect of straining almost every other component in your system, since it all derives from it. More expensive motherboards can keep a constant PCI-E clock or allow you to set different memory clock ratios to allow you to overclock better.
The good thing for you is that an AMD Black Edition chip has an unlocked multiplier. You can just go into your BIOS and just increase the multipler, it's that simple.
Bump it up a notch and each time, boot back into windows, run CPU-Z and Speedfan and watch your temperatures. Run benchmarks and stuff to make it work hard. If you get problems, or pass 55-60C, lower the multi until you get stability and an acceptable temperature =o