thnx sceadwe!
in the meantime I did some solution work and found something on the windows website:
1.Exit all Windows open on your Vista computer.
2.Click Start, click All Programs, and then click Accessories.
3.Right-click the Command Prompt option and then select Run as Administrator from the right-click menu.
4.Type the following command in the Administrator: Command Prompt window and then press Enter.
net stop WuAuServ
Note: View the Command Prompt messages to ensure that the service stops successfully.
5.Next, click Start, select Start Search, type %windir% and then press Enter.
6.In the folder that opens, search for the Software Distribution folder.
7.Rename the folder to Software Distribution Old.
8.Go back to the Administrator: Command Prompt window, type the following command and then press Enter.
net start WuAuServ
Note: View the command prompt messages to ensure that the service starts successfully.
9.Check the Windows Update Web site to see if you can update your Vista computer now. The Windows Update Software distribution folder is created again when the update starts
AFter I did this the update service started and worked fine! there was one update in line which had someting to do with windows defender after I installed this update (KB915597) I tried to update again but it failed giving the exact same code 8000FFFF error as before!