|"Do I need to install 64 Bit?"|
Yes, you have 16GB RAM. 32-bit can only use 4GB but will only recognize 3-3.5GB due to VAS mapping. 64-bit will allow ALL the RAM to be recognized & useable. Try this, go to the start menu, right click on Computer, then click Properties - what does it say for 'installed memory'?
Also, check your CPU temp in the BIOS. It should be in the upper 20s - low 30s at idle depending on room temp. If it's considerably higher, the heatsink probably wasn't installed correctly.
BTW, where's the power supply specs? And which anti-virus program are you using?