Since you have vista on the computer now, the upgrade more than likely will not work because you can't upgrade to an operating system that has not been recognized by the upgrade program....meaning that vista is newer than the upgrade.

Not to worry though....but you must be sure this is what you wish to do in the case of hidden partitions.

Use a boot utility program to wipe vista completely clean and then reset the partitions if you wish or leave them....

Now boot to the upgrade CD and follow the set-up proceedures...use the ME disc or a W95, W98 NT, 2000 to prove that you have the right to upgrade.