Black Windows Vista Login Screen. Please please Help

[psand]

i run disk defrag with diskeeper yesterday and also run disk cleanup. i started my laptop this morning and it dosnt start.i tried startup repair; initially that didnt work cos i couldnt load the drivers for my drive. but it worked eventually. what i did, i still do not know. right now the problem is that after windows starts, the bios screen appears, the vista loading screen appears, BUT AFTER THAT I GET A BLANK SCREEN with just my mouse cursor.i tried ctr+alt+del that didnt work. i tried using the ubuntu live cd to access my C:, i cant . i get an error that the disc cannot be mounted.
startup repair doesnt find any problem and says windows is ok. system restore says there is no restore point available, even though i knw i have one restore point i created just before i turned off the laptop last night.
everything points to the fact that the OS is loading up. but where the login screen should be is blank.
please help me. reinstalling my OS is not an option.i have my final year school project in there, no backup.
please.
thanks

[psand]

oh and i forgot to add. neither does safe mode too work.
does windows vista not have an OS repair utility like xp??

[MARKBINGO]

I have the same issue.
It seems nobody on this forum knows an answer.