Black Screen With Cursor In Windows Vista.

Hi Everyone

I'm Having some problem with my computer its been a week tried everything i could.My computer is showing black screen with cursor. i cant access to safe mode or anything else.comes back to the same process with black screen with cursor.This Is what i did So far :

1.Tried Removing the Memory since 1 have two 2gb memory ram.
2.pressed shift 5 times and nothing showd up
3.Removed all the usb's wires are connected to the pc
4.Tried system Restore but it getz me an error(System restore failed due to an unspecified error catastrophic failure(0x8000FFFF)
5.Star up errors fix:


> Problem event Name: Startup Repair V2
> Problem Signature 01 : external media
> Problem Signature 02 : 6.0.60000.16386.6.0.6001.18000

> Problem Signature 03 : 6
> Problem Signature 04 : 589833
> Problem Signature 05 : no boot failure
> Problem Signature 06 : no root cause
> Problem Signature 07 : 0
> Problem Signature 08 : 2
> Problem Signature 09 : Wrp Repair
> Problem Signature 10 : 87
> Os version : 6.0.60000.2.0.0.256.1
> Local ID : 1033





Plz Guys Help Me.I dont wanna loose the Data.Thanks :)