Well, I could wave my magic fairy wand and hope that it fixes everything.
Or you could actually give even the faintest hint of your system information and what exactly you did to upgrade, paying particular attention to what brand and speed of RAM you used exactly and what kind of memory timings you've set it to.
Knowing information on your power supply as well as the voltages on each of your rails would also be rather useful, as would what motherboard you're running it all on.
PC Repair-Vol 1:Getting To Know Your PC.
PC Repair-Vol 2:Troubleshooting Your PC.
PC Repair-Vol 3:Having Trouble Troubleshooting Your PC?
PC Repair-Vol 4:Having Trouble Shooting Your PC?