I run the program unmodified (no updates or extra plug ins). It goes through the entire process with 0 errors & 1 warning (using Windows XP OEM disk). It completes and states ISO has been created. Problem is there is no ISO file. I took the default the first time on where to save or create the ISO file, then tried the desktop, my documents. It states it has created it - but nothing. I have uninstalled/re installed to no avail. Any ideas?

By default, Windows hides known file extentions... set yours to show all file extentions, I suspect the file is indeed there.

Nope not there. I was attempting to create this ISO file on a Vista machine. Switched to an XP machine and all is well.

Interesting you didn't think to mention it was a Vista system since that is certainly vital info...

Right click on the UBCD4WinBuilder.exe and select "Run as Administrator" ... or better yet.. disable UAC and while building Windows Defender since they are known to cause issues with programs in general... you can always re-enable them later if you must.