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1. Boot off the Vista Install CD
2. Select “Repair your computer” to continue.
3. Proceed with the repair process by choosing “Startup Repair” from the list.
4. If that fails Go ahead and select “Command Prompt” from that list.
5. Type:

bootrec.exe /fixmbr
x:\boot\bootsect.exe /nt60 all /force
del C:\boot\bcd
bootrec.exe /rebuildbcd
shutdown -r -t 0

6. If that ALSO fails:
Go back to the command promt as above and now type:

bootrec.exe /fixmbr
x:\boot\bootsect.exe /nt60 all /force
del C:\boot\bcd
bcdedit /createstore c:\boot\bcd.temp
bcdedit.exe /store c:\boot\bcd.temp /create {bootmgr} /d "Windows Boot Manager"
bcdedit.exe /import c:\boot\bcd.temp
bcdedit.exe /set {bootmgr} device partition=C:
bcdedit.exe /timeout 10
del c:\boot\bcd.temp
bcdedit.exe /create /d "Windows Vista" /application osloader
bcdedit.exe /set {c0dfc4fa-cb21-11dc-81bf-005056c00008} device partition=C:
bcdedit.exe /set {c0dfc4fa-cb21-11dc-81bf-005056c00008} osdevice partition=C:
bcdedit.exe /set {c0dfc4fa-cb21-11dc-81bf-005056c00008} path \Windows\system32\winload.exe
bcdedit.exe /set {c0dfc4fa-cb21-11dc-81bf-005056c00008} systemroot \Windows
bcdedit.exe /displayorder {c0dfc4fa-cb21-11dc-81bf-005056c00008}
bcdedit.exe /default {c0dfc4fa-cb21-11dc-81bf-005056c00008}