i have MSI K8N Neo4/SLI Motherboard but i dont know what processors go into it.
I play alot of games and i tend to multitask while playing (watching youtube while playing Wow)
i have NDIVIA GeForce 8800 GTS with 2gb of ram.
i need a new processor / or if i need a new motherboard
MSI K8N Neo4/SLI is an AMD socket 939 MB. Socket 939 was discontinued years ago. The 939 processors are becoming hard to find and finding a new 939 MB is near impossible. I can link an OEM 939 processor, but no new 939 MB's I know of are available with etailers. Your current system CPU and MB are basically Fleabay items. Try posting in Homebuilt Section for idea for a new build. I wouldn't recommend spending much money on that system you have currently.
Yes. Your old video card would work. If you have ddr pc3200 ram, then the slower 939 cpu would work. But if you have to buy memory, then I would go for a cheap board with am2 or am3 cpu that uses ddr2 or ddr3. Don't go cheap on the ram. Get some regular non ecc low density such as corsair, crucial, or kingston. One more alternative is to shop for a used cpu or ram on craigslist or anandtech's "for sale" forum.
Don't overprice your board. If you haven't tested it, let the buyer know. I would ask around $35-40 for it, unless you want to let someone else test it for themselves in yours or their homes. But most folks just want to meet somewhere to do the exchange. Craigslist is free. I save the email file they send you to use the "delete" function when the item is sold, or to start a new ad every day. The ad is bumped down the listings quickly, so I post a brand new ad every day until sold.
For the motherboard-cpu, you need to list a budget, and whether you will use ddr2 or ddr3. Newegg has several combo deals with some of the dual core regors that use ddr2, and one combo that comes with 4 gigs of ddr2, board, and regor 240 for $217. I use frys combo specials. They have a 425 tri core amd with gigabyte board for $69.99 after rebate now. The board may even unlock the 4th core.