Well if it was me, I'd copy the elements from your original timeline into a new HD timeline (as opposed to nesting it), scale to frame size and make any adjustments from there, then export. If that's too much work, you can buy the Instant HD plugin which would up-rez the files from your nested seq.
You can also look into 'up-converting' the original but without good encoding hardware the results are often dissappointing.
My 2 cents anyway
Does PPro allow more than one instance (can I have it open twice at the same time)? Or are you saying that it will let me select the contents of my SD timeline, close the SD project, open an HD project and then paste into that?
That would work exactly how I'd hoped. I'll give it a try.
Hmm, I see that you are using PPro 2, not sure if you can have both timelines in the same project. I can in CS4. Well give it a shot!
Unfortunately you can not do that in PPRO2 (easy in CS4 where you can have multiple varied sequences in the same project).
Thanks for all the answers.
I plan to upgrade when CS5 comes out. The upgrade to the project can wait until then.
It worked. I created an HD project, saved it, and opened the SD project, clicked on the timeline, hit CTL+A to select all the contents of the timeline, closed the SD project, opened the HD project and pasted the contents into the timeline.
This is in PPro 2.0, so it will let you copy from one project, close that project, then paste into a different project.
Thanks again to all who replied.