You can do it from the command line:
Code:
diskpart
sel disk 1
sel part 1
detail part
This should print something like this:
Code:
DISKPART> detail part
Partition 1
Type : 07
Hidden: No
Active: No
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
* Volume 4 D NTFS Partition 112 GB Healthy
Then type:
To make it the active partition.
typing should display the same as above once more, but this time active = yes.
Type to quit the command-line partition manager.
Note: the above assumes the Vista partition is the first partition (part 1) of the first drive (disk 1)