PC freezing up randomly

Lately my computer has been randomly freezing or getting massive lag and lots of times takes a while to load something or the program stops working, and some times overall everything stops working and the hdd indicator stays solidly lit. I usually reset and works from then on. I suspect my hdd as its been refurbished by seagate already and when i let everything just sit at idle for a while or just listen to music, ill come back and try to change song or start doing something, the hdd will make a clicking noise then everything is fine. I think its prob a power saving feature, but i dont think it should be doing it. Usually its just the hdd where itunes or something stalls, but once in a while it'll be the OS and everything just stops, which the OS is on an ssd and its been refurbished returned from OCZ, but was replaced by a newer model than wat i returned.

Alot of times beside when a program lags, where the hdd may be the issue, its usually lag and eventual freeze of Windows right when i log on and start a program, like itunes, google chrome, firefox, etc.

Specs in sig, but hdd is a Seagate Barracuda 1.5Tb 7200rpm ST31500341AS, SSD is a OCZ Vertex 3 60Gb VTX3-25SAT3-60G, running Win 7 Pro 64bit. Seatools say both pass SMART test and other quick tests. Any help is appriciated
 


My apologies, skim read the last part. LOL

Ok now test your RAM.

Create a bootdisk with memtest on and boot into it, let it run at least 3 passes.

http://www.memtest86.com/

Click "free download" and follow the instructions on the site.