Problems with Windows 7

Hello,

Could you help me? I can't start many applications from my Windows 7 desktop. It often freezes. I have to start Windows in Safe Mode to get anything done. Even then, some applications like Firefox freeze.

Specifications:

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Home Premium, Service Pack 1, 64 bit
Processor: AMD Athlon(tm) II X4 620 Processor, AMD64 Family 16 Model 5 Stepping 2
Processor Count: 4
RAM: 7935 Mb
Graphics Card: NVIDIA GeForce 9100, 256 Mb
Hard Drives: C: Total - 598081 MB, Free - 376624 MB; D: Total - 12295 MB, Free - 2227 MB; F: Total - 1430796 MB, Free - 729603 MB;
Motherboard: PEGATRON CORPORATION, VIOLET
Antivirus: Microsoft Security Essentials, Disabled