Windows 7: Windows explorer stop working

hi
when i log off my computer and then log in windows explorer crash and everthing freeze!! and i have to rest my system
windows 7 x64 ultimate (updated)

i tryed sfc /sc... and memory check etc but nothing worked for me
here are some erroe detail :

1.Description
Faulting application name: Explorer.EXE, version: 6.1.7601.17567, time stamp: 0x4d672ee4
Faulting module name: ntdll.dll, version: 6.1.7601.17725, time stamp: 0x4ec4aa8e
Exception code: 0xc000041d
Fault offset: 0x00000000000532d0
Faulting process id: 0x102c
Faulting application start time: 0x01ccd919eb91fedd
Faulting application path: C:\Windows\Explorer.EXE
Faulting module path: C:\Windows\SYSTEM32\ntdll.dll
Report Id: 4b172990-455c-11e1-8984-0026b91d7af4



2.Description
Faulting application name: Explorer.EXE, version: 6.1.7601.17567, time stamp: 0x4d672ee4
Faulting module name: ntdll.dll, version: 6.1.7601.17725, time stamp: 0x4ec4aa8e
Exception code: 0xc0000374
Fault offset: 0x00000000000c40f2
Faulting process id: 0xcb0
Faulting application start time: 0x01ccd5db31aa4f2a
Faulting application path: C:\Windows\Explorer.EXE
Faulting module path: C:\Windows\SYSTEM32\ntdll.dll
Report Id: ce3b3933-41ea-11e1-ba19-904ce5caf6b9

Can't say for sure what is happening but prima facie it appears that the HDD is packing up.

Since when has this started happening? Are you hooked to another HDD in addition? If yes then unplug this drive and try installing Windows 7 on the other HDD.

one hdd in use and cant try other one I dont know exactly when and what cause but if i open several folder and then log off/in it happen

in some cases mouse work and i can rest explorer,exe but mostly everything freeze