ugh, Jetway. Looking at that boards product page the BIOS hasn't been updated since 08. Also, their CPU support page is a pain in the butt. Anyway, a 7750 will not work in that boardhttp://www.jetway.com.tw/jw/support_motherboard.asp?supportid=262&socket=AM2
You should be able to use a Windsor 6000+ though but that's about it. If you want something more modern it's best to look at building a new system. If you currently have a lower clocked dual core you may want to consider overclocking it for now to extend the usefulness of your system.