thats your CPU support list, you wont need a bios update to support and CPU on that list but you also have limited options. What do you use your system for mostly? You are going to want one of the E7xxx or Q6xxx, i wouldnt go much lower if you want your system to last for a while without another upgrade.
whats running slow? It may or may not be the processor. You dont have a very fast HDD and 4GB of ram will generally provide a decent improvement over 2GB so there may be better options than a processor upgrade. Also make sure that you clean out windows, crap builds up over time.