How to reinstall Vista Home on Dimension E520

I know since I've done this before, it's possible . . . but I can't for the life of me figure out what I did a few years back.  Our Dimension E520 won't boot into Vista, System Restore hasn't worked, and various startup repair attempts have not worked either.  Seems to me the only available option is to reinstall the operating system from the factory partition, but none of the support documents I've found tell me how.

Since the system was shipped with Vista installed we never had an installation disc, just the "D:\" partition.  Can someone point me in the right direction?

{As an appendix of sorts, what I am ultimately after is to recover the data (files, e-mails, Firefox passwords, etc. etc.) onto our much newer Windows 10 machine.  Reinstalling the operating system will obviously help but other ideas on transferring a decade's worth of data are welcome.}

Thanks!