Advice on what to upgrade

[pieman711]

I've had the same set-up for about 6 years now and with all the new steam games (especially metro 2033) it is starting to show. I would like some advice on what will be holding back my gaming performance the most, and what I should be considering replacing it with.
I've got an ATX case with 650w PSU. It has a full sized ATX mobo (ECS elite group NF650iSLIT-a) and Intel® Core™2 Duo CPU E6750 @ 2.66GHz. I have a nvidia 8800 GT and 3gb of ram. I

The motherboard is probably the most annoying thing at the moment. The built in USB ports all dies spontanetously about 4 years ago (in Windows and Linux so I think it is a hardware thing) and for some reason the BIOS has never been able to boot from USB, just CD.
I want to upraged the MOBO but is it worth getting a new processor as well or shall I save that money and put it towards new ram or graphics card?

Any suggestions for any makes or specs of the replacement bits?
Thanks guys

[Yellow Pasque]

If you're a gamer and it's been 6 years, it's probably time to redo the whole system. However, if I was going the upgrade route, then I would keep the CPU and I wouldn't buy a new mobo (unless I could get a Socket 775 mobo for a good price). The money is better served getting another 1GB stick of RAM so you can take advantage of dual channel memory (assuming you have 3 x 1GB sticks) and upgrading the GPU (stay with nvidia).

[pieman711]

I think I already know the answer to this one but, is there any point in looking in to the SLi route and getting another 8800GT or should I start again and get a more recent graphics card? At the moment Metro is just about playable with the video settings set to the lower three tabs. What is the best performance anyone has been able to get from it?