Windows7/64 freeze on desktop

Hey all!
My computer had been acting up not starting easy I'd have to leave it off for a long time for it to restart correctly it seems.
Any who I swapped it out with my other computer, and it sat there for about five months. So today I go to start it and everything starts up normal, BUT when it reaches desk top it will not let me open anything? I tried clearing CMOS, and resetting the BIOS. No dice, it seems like it is running OK just will not let me do anything once in desk top.
any suggestions are greatly app., I'm sure its a no brain-er I'm just over looking some thing simple. I will go in and try safe mode(witch I haven't done yet) but wanted to post up and get some feedback. Plus its an excuse to scan the forums and brush up!
Cheers!

Hey Richc,
Same thing in safe mode, tried to start it in repair mode same thing. Tried to boot from the OS dick same thing, the screen appears but that is all. Completely frozen.........
Keep um coming!

TY again!
I'm learning towards a hard ware issue, as it freezes in repair and the same with the system disk too. I tried swapping out memory (DDR2) I get no boot now.
So I'm gonna replace the mem. and then I may re-seating the CPU, though I'll check my voltages in the BIOS. Not sure if they have a hardware section, if so Mods feel free to move this I'll up date ASAP!
Again Thank YOU Richc and keep the idea's coming!!

OK so I put back the original RAM and ran Memory test, my P45 motherboard has it built into the bios(love it). Memory is not the issues, not one error. Re-seated the CPU, same thing.
I'm gonna try a 24hour CMOS clear as it will woirk, it will freeze even when the OS disk is installed into it.
Only other thing is to remove the motherboard hook it up outside the case, see if shes grounding out some where.
Thank You Richc!
Again Keep um coming!!