Comp freezing in XP and DOS..lil' help?

I am running an asus M2NPV-VM motherboard with 3gb of ddr800 ram. So here is my issue..I got new memory recently (patriot brand) and put it in with the current memory I had. Everything was fine and dandy then 2 days ago my computer stoped recognizing my usb ports and sound card..It then procedes to lock up at random times in windows xp (pro) AND in dos. My 1st inclination was that my cpu is over heating..so I air dust the fans and get good circulation going and noticed that my temps were pretty good (40-50c) I then thought it was a gpu issue but when I got the lock ups in dos I ruled that out as well. I then thought it was a memory problem..I tried running memtest twice but my computer will freeze in the middle of it. Is this a power supply issue? Is my motherboard just shot? or can this all be fixed by doing fdisk?FYI the usb ports are recieving power but not sending/recieving data (as discovered by charging my cell phone)..Any advice is most welcome. Comp freezing in XP and DOS..lil' help?
I should also note that I know that mixing memory can be an issue but I have never had a problem before..I also took out the new memory and just left in the old...same issues.Comp freezing in XP and DOS..lil' help?
It's fairly likely the RAM. Try not mix and matching the RAM (never a good idea) and see what happens.Does it run fine with only the old RAM? Does it run fine with only the new RAM?
I put just the old ram back in...still the same issues..I have not tried it with the new ram seeing as how my computer didnt have this issue untill it was put in...
Try with just the new RAM. Also make sure all the voltage and timing settings are correct for the RAM in the BIOS.
Try it with just one stick at a time and see if it gets better.Mixing RAM brands can be bad, but considering that RAM manufacturers buy there RAM chips from different companies, even if you bought the exact same RAM, depending on the brand, it could be different RAM. I would not worry too much about it, I have mixed RAM brands(not curently, but many times in the past), and have never had a problem doing it.
From my experience issues with USB ports and freezing typically indicate problems with the power supply. If the ram was bad the PC would crash/restart rather than freeze.