DVD-R to DVD+RW on my computer

[Jumpshot44]

I am trying to copy some old home videos on DVD-R's to DVD+RW's on my computer. Using my Sonic program I go through the whole process but when I try to copy, it tells me my destination DVD doesn't have sufficient space. This is ridiculus because there is only 1-2 hours of video on the DVD-R. The DVD+RW I am trying to copy to is a Memorex with 4.7 GB open space. This was an expensive disc to buy and in SLP mode can record up to 360 min. Why does my computer keep telling me I don't have enough space? Suggestions?

[mats.hogberg]

If simple DVDDecrypter ISO read/ ISO Write procedure (which is basically the only method to use to backup disks) gives you the same error, I'd say its down to the slight capacity difference between + and - formats.
Forget about disc capacity in terms of time - that's just some marketing bull for the ignorant. Same for 4.7 GB - another marketing ploy. 4.37 GB is the regular DVD-5 capacity (in computer terms where k=1024, M=1024 squared, G=1024 cubed).

/Mats