Hello corvair,
Unfortunetly, without access to Vista, you can't run a Diagnostic Report. Without it there is really no troubleshooting I could do. But I do have a few suggestions.
The first thing I suggest would be to call your Local Activation Call center and confirm the Product key is good (i'm sure it is, since it worked before, but just in case). Also, be sure you have read the Product key off the Vista Retail box (or off the sticker on the side (or bottom) of the computer) correctly.
Activation Call Center list:
http://www.microsoft.com/licensing/resources/vol/numbers.mspx If the key is good, then the problem you are seeing is (most likely) not a problem with the Product Key, but with Vista itself (maybe a bad install) and since you have not been able to load into Vista since you last installed it, I would qualify the problem as a Product Installation related issue. Microsoft supports all Product Instalation issues at no cost. Therefore, I suggest contacting Vista support at (800) 936-5800.
Sorry I couldn't be more help,
Darin MS
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