A couple of other options...store back to digital tape or burn to DVD as data files. I agree, storing to hard drive is probably the most convenient and, per gigabyte, less costly.
As for rendering for burning to DVD, recomend you use the MPEG-2 DVD template in Vegas 4 but go in and change the quality setting under the video tab to best (click custom button on template).
If you do a search on archiving you will find a thread that Spot had commented on. Basically the most ecnomical method is to archive to an externall drive, tape is more expensive.