System beep warning and no POST screen. Help!

I tried to connect my guitar through a processor on "line-in" and as soon as I did it, my pc, which was perfectly alright, stopped working.
I gives me "beeeep beep beep beep" on award BIOS and the video doesn't show. To figure out of if one of the hdds not working, I took the motherboard out with the min cimponeneys required for a system to work ie processor, mtherboard, ram, graphics card, keyboard.
Now I tried different combinations of the two ram modules I have on the 4 slots but to no avail. I ran out of ideas to figure out which part exactly is causing the problem. I changed the gfx too but no improvement. I'm willing to forgo the part and purchase a new one but I don't know which is the part that isn't working! Ram has a life time warranty n gfx is inside warranty time but if mb is the prob, can you guys suggest a good medium range mb that can be compatible with mac (like no nvidia chipsets, etc). The following is my config

asus p5n e sli
core 2 duo e8400+
2x2gb ram 800mhz
nvidia gt220 gfx 1gb

ps: I don't want to upgrade the processor cuz of socket n keeping up with latest mbs, I will use it for another year only so I need mb for this processor !
please help, thank you

P

The beep code you described - one long beep followed by three short ones - usually indicates a problem with the graphics, but I notice that you've already tried changing the card. As your mobo doesn't have onboard garphics, you can't try that.

It's surprising that pluggig in a guitar effects processor should damage a motherboard. Have you tried clearing the BIOS?

Though I've tried it yesterday, I've tried it again today and it worked. I had a gs8400 b4 and upgraded it to gt220, now I've changed it back and it started giving a single short beep and everything goes well... thx for checking on that again

just a small info, I've purchased gt220 like a 6months b4 and I was wondering if the warranty would enable me to get a new card ? or instead, can I add a few more grand and get a btr one?