While you will lose resolution, cropping 4:3 video and blowing it up to 16:9, I've found the results, out of Vegas, are quite pleasing. I've done this with some ancient (vintage 1982) VHS stuff and it looked very good.

If going 16:9 to 4:3 is "pan and scan," then I call 4:3 to 16:9 'tilt and scan.'

Set project to NTSC (or PAL) DV WIDESCREEN
Put 4:3 video on timeline
select Pan/Crop tool and use 16:9 preset
move the crop position to the portion of the frame to keep
if needed, use keyframes to move the position with the program
Render using NTSC (or PAL) DV WIDESCREEN template

I've had a lot of fun with it!

Blowing up my analog 4 x 3 to 16 x 9 was a disaster in V5d. Everything got wormy. The small noisy pixels got converted to large noisy pixels.

JJK

Most widescreen TVs will blow-up 4:3 to 16:9. I've found that Vegas will make that transition better than than the TVs I've seen. Also, there is the advantage, in Vegas, of being able to continually select the portion of the frame to keep ('tilt & scan).

There are ways to deal with analog video noise, though none are as good as one might desire.

I would rather view most 4:3 content in a 4:3 aspect... But... Occasionally... I have enjoyed converting some old clips to 16:9. Is it perfect? Heck, no!!! It's a compromise that can, sometimes, be pleasing.

Of course, if the client wants it 16:9, then there's no choice.

Thanks for the answers everyone. I will make a small video file + play about with it before the wedding to make sure I don't chop the brides head or feet off.
I'll post again if I have any problems.

Bye.

Just a note here: If you want to resize "video", there may (or must) be a loss of quality. If you plan to resize Computer Generated Images (CGI) previously rendered , for instance, as TGA (Targa) sequence files, there will be no loss of quality at all, even though you'll have to work a bit moving the resized screen to have all objects centered in the safe area. ;)

If your planning to shoot 4:3 and later crop to 16:9, it wouldn't be a bad idea to mask your wiewfinder and or reference monitor for the desired aspect... That way you always know that your framing is right.

In the past I've resized interlaced 4:3 to 16:9 with no problem. I can't do it anymore though. The interlace pattern gets resized and no longer matches the interlace lines on my tv. The resulting look is "wormy" I guess you might say. Vertical lines are no longer straight. They look more like some kind of sine waveform. Since I'd done it successfully before I figured it was some kind of version 5.0d bug. I went back to a previous version (5.0b I believe) and all was fine for a test 16:9 render or two. Then about a week ago, I wanted to do a 16:9 version of a 4:3 project. No version of Vegas would do the 16:9 tranform correctly. I tried it both manually and with the Ultimate S plugin. I tried it with versions 5.0a, 5.0b and 5.0d. No matter what I tried, the interlace lines were resized and the results were unusable. I ended up doing the aspect ratio change in VirtualDub using a fields unfold filter, a lancos resize, a crop and a refold fields filter. I have no idea what is going on here. I know that when I first tried the Ultimate S aspect ratio change I was blown away by how well it worked with interlaced footage. Now I find it quite useless.

Anyway, with the newest version of VirtualDub and the stock deinterlace/unfold/refold and lancos resize filters, I can still do this transform, though quite as cleanly as I once did with Ultimate S and Vegas directly.

I'm having great fun with this. The results so far, bearing in mind that I am poor and using Vegas 3 in Win 98 SE without DVD Architect:-
I can get the 16:9 effect by either setting the template to 16:9 DV or by using the pan and crop. If I use both it letterboxes left and right as well as top and bottom. Pan + crop is better as I can keyframe it to keep heads instead of feet. If I re render again to MPEG 2 DVD file with widescreen i get coneheads in a square box. If I render again to MPEG 2 DVD file without widescreen I get something that plays back on the PC OK. When I give it to Nero to burn it to CD (mini DVD) it tells me it is not a valid file format. If I give it to Nerovision Express 2 to re transcode it, it freezes.
If I use Vegas and tools/burn CD/multimedia CD/DVD Pal ; it will, but the sound of the finished disk on the PC is like a pneumatic hammer and the picture quality is crap.
If I keep it as a widescreen avi file (using the PAL DV template) and render as avi Pal DV, not widescreen, then Nerovision Express will burn it to a CD as a MiniDVD and it will play very well on both my PC's, picture quality could be better but it's acceptable. However, if I try to play it on a standalode DVD player I am back to the pneumatic hammer effect.
Is this because:- a, the mainconcept video codec is faulty?
b, my DVD player is faulty?
c, miniDVD on a CD in a standalone player will always pneumatic hammer the sound?
d, I've got it all wrong somewhere before I get near burning it to a disk?
e, My source material is in some way faulty?
f, none of the above,
Excuse the length of this rant but I have a large stack of new coasters that I don't need and I'm getting ready to embed them in a small furry animal, or one of my kids if I make many more of them. This is also why I am making MiniDVD on CD instead of using expensive DVD's until I have this right?

Help please.

It all works.
The answer. Don't use mini DVD on CD, what you lose is apparently the sound quality.
I re rendered 10 identical 2 minute clips to DVD with all of the possible permutations of widescreen and render to widescreen/ pan+crop etc and all of them worked as far as image and sound quality are concerned.
Small furry aminals and children are safe for the time being.
Thanks to Phil A and all others who contributed