Yes, you can do this to preview an AVI movie quite nicely. You need to run DivFix or some such utility to reindex the AVI before you can view it however.

I just tried this on The Grinch/Jim Carrey movie that I am only 50% complete in.

The biggest bother is figuring out which file it is in the Xolox\Temp folder. So as to not interrupt the download in progress, I copied the .XLX file first and renamed the copy to temp.AVI

Do a search on Google for DivFix if you need it. I used version 1.05 which is available from DOOM9.ORG