Vista - explorer.exe crash/ sleep mode disabled

ok i am currently running a system with these specs

OS: vista home premium

CPU : dual core 3.1 ghtz amd athlon

MB: ASUS M2A-VM

Ram : 8 gig installed and recognized.

Video : Nvidia GeForce 9600gt 512

Sound : Mobo


the issues that i am have are these,

As of today i completely wiped the computer HDD by doing a reformat and doing a clean install of the OS. what is happening is that explorer.exe will crash suddenly without any warning and no error will appear other than the following messages

explorer has stopped working
windows is checking for a solution

then nothing happens except the option to close the popup.
I have been researching this issue since it started about three weeks ago and the general concensus was to roll back the computer. now that i have done that (reinstall completely/reformating) i am still getting this occurence.

the second thing that has become a regular occurence is that the sleep function has been disabled completely. when i hit the sleep button from the start menu the computer will act as if it is going into sleep mode then almost instantly bring itself out of sleep. i have check all the options within power management and they are as they should be, i have checked the bios as well and it has not changed since i first set it up for this system.

please any help whatsoever would be greatly appreciated.

another thing this is not an older computer it was bought just in december.