I think more info is needed about: your version of Nero and which Nero
app you're using, the exact error message you get, and the nature/size
of your ISO. Is it a DVD movie/video you're burning, an application,
etc? Also, I'm assuming the blank DVD you tried isn't bad?
Not all ISO's are alike, and not all DVD burners can do all ISO's. You
may also need to do a diagnostic on your ISO file as well, as there
could be a problem there, corrupted, etc At this point, I'd recommend
trying another DVD burner that can do ISO's. Also, it'd probably be a
good idea, if you want to spring for them, to use rewriteable DVD's so
you won't be making a bunch of coasters as you try out apps.
Normally, I would suggest CDBurnerXP [works on Win9x as well], which
does an excellent job burning ISO's, but don't think it does DVD ISO's.
http://www.cdburnerxp.se/features.php
I *think* BurnAtOnce [freeware] does DVD ISO's, but you need a freeware
[for private,educational/research] addon, ProDVD:
http://www.burnatonce.com/index.htm?faq
I've never used BurnAtOnce for DVD ISO's, however.
An *excellent* freeware to try is DVD Decrypter to burn your ISO.
Here's a tutorial that shows you how, directly from your ISO file.
Tutorial also illustrates using freeware prog Folder2ISO [you've
already got this part, sounds like]:
http://www.afterdawn.com/guides/archive/burn_dvd_folder_dvd_decrypter.cfm
Here's another tutorial:
http://www.mrbass.org/dvdburn/
I'd also recommend checking out
www.videohelp.com for more excellent
tutorials, etc on ISO burning. It'll give you some tips, specializing
obviously in burning video files, but the same general principles
apply.
www.videohelp.com also has an interesting comparison between Nero,
ImgBurn and DVD Decrypter, specifically for burning video, but some of
the same ideas can apply to burning other sorts of files.
http://www.videohelp.com/forum/viewtopic.php?t=258338
Too, you can use a tool such as the freeware/shareware tool ISOBuster,
to see what's in your ISO, extract, etc.
www.isobuster.com
Though I've never used it, I've heard that the freeware TugZip also
does a good job extracting ISO's.
http://www.tugzip.com/
Once you successfully extract your files, then Nero or whatever DVD
burner you choose might stand a better chance of burning your DVD.
Most of the above sites also have user forums where you might get more
help by posting your query there, or searching for others with similar
Nero/ISO burning issues.
There are quite a few tools for burning or working with ISO files, as
you can see from doing this Google search for freeware DVD ISO burners,
& also check a.c.freeware for recommendations via groups.google.com.
Some, of course, are better than others, a few come with unwanted
ad-ware, etc.
http://www.google.com/search?hl=en&lr=&safe=off&q=dvd+iso+burn*+freeware&btnG=Search