Yes, you can shrink a partition via your current Vista installation, by right clicking on My Computer and going to Manage. Then select Disk Management. Then select the partition you wish to shrink (ie your current one). Select its size, and complete. You will now have the second allocated space for your other installation. Use EasyBCD to add a second entry to the Vista boot loader. Hope this helps. We can disagree on sound, but i doesn't mean we cant help each other out right?
Easy BCD
http://neosmart.net/dl.php?id=1
1. Set a restore point.
2. Back up critical data
3. Right click on My Computer.
4. Select Manage.
5. Select Disk Management.
6. Right click on your current partition (or the one that you wish to shrink)
7. Select shrink and select by how much.
8. Apply.
9. Restart and boot into Vista DVD
10. Install Vista on the unallocated partition
11. Enter either vista installations
12. Use EasyBCD to add, rename, etc the Vista boot loader options.
done.
