Let’s try to repair your PC using Recovery DVD.

Insert the Windows Vista Recovery DVD into DVD drive.

Select command prompt
At the command prompt type the following :

notepad

and press Enter.
The notepad opens. Under File menu select Open.

Open your DVD disk and find install.wim file (it should be in “sources” folder). Copy this file on the drive (don’t use system drive!)
Create a folder named wim on the same drive.

Select command prompt
Type in the following command :

Dism /Get-WimInfo /WimFile:D:\install.wim

and press Enter.
where D:\ is a letter of drive (not system!)

then

Dism /Mount-Wim /index:2 /WimFile:D:\install.wim /MountDir:D:\wim

and press Enter.
where /index:2 is your version of windows Vista, D:\ is a letter of drive where you saved install.wim file

Now we have all system files.

Type in the following command in command prompt:

sfc /scannow /offbootdir=C:\ /offwindir=C:\windows

and press Enter.

where “offbootdir=c”-directory with system files from recovery disk (in the “wim” folder)
“offwindir=c”- directory where your OS installed

After sfc finish it’s job, type in the following command in command prompt:

Dism /Unmount-Wim /MountDir:D:\wim /Discard

and press Enter.