Using 80min CDR as 74 Min?

[tonyb]

I am using an HP8100i CD Writer which HP says will work with 80min CDR but only use 78 and a bit mins. I am trying to use the HP Simple backup software which works OK with 74 min disks but bombs out when using the cheaper 80min disks. I would like to solve this problem before 74 min disks become obsolete or even more expensive!

I tried HP but so far they are saying "that is the spec"

Any ideas?