Processing Speed Trouble

[Alphadorum]

CPU: Amd 6300 FX
GPU: GeForce GTX 470
Gigabyte Mini ATX 78LMT-USB3
4GB RAM

My PC when I orginally built it was processing and able to open apps and programs very fast and now it sometimes takes 15-20 seconds to open a program. Ive cleared memory and disks fragments and uninstalled quite a few programs and I just replaced the thermal paste just to make sure it wasnt the problem but nothing seemed to change. I am new to building PCs and I really could use some help with figuring out the problem. Thank You in advance!

 

[Alabalcho]

Make your PC like new - reinstall Windows from scratch, then install only the apps you really need.

 

[Tradesman1]

Check and cleanup start up of unneeded items, many just eat up DRAM and slow things down, defrag, remove excess programs and files as you've started