Ok, i set the D:, which should be a HP_Recovery drive as the active drive, thinking that it would do a system recovery. But the files on the D: must have been deleted and now Vista won't boot!!
Usually to do a recovery you need to boot into the recovery console. Which is something like F8 (during loading it should breifly give you what key to hit to enter the recovery console).
The recovery console isn't a separate drive, but a partition on the same drive as what you are probably working on right now (this is the normal setup for store bought computers). So i'm not sure what you mean by setting D as the active drive.
Did you go through the recovery options? What prompted this? Maybe we can walk you through fixing the issue.
Just a word of warning - going through HP's recovery steps WILL DELETE ALL AND ANY FILES ON YOUR COMPUTER. It will set the computer back to its original state.
There were 3 different steps listed. Not 1 of them worked? If not get the media on order from HP. Your Recovery drive is gone and there is no way other than a format and reinstall with the Vista Media to restore your PC.