Compression question - estimates welcome

I'm a new user of Acronis True Image 9 - that is, I'm trying to become a new user. On my first try of a backup, my CD unit doesn't want to be opened after it has been written to. This is idiosyncratic to this machine, and I've found a way to get around that when I'm just copying things to the CD-RW, but it involves leaving the program and then starting it again. This won't work with Acronis. So I decided to try another target medium. And as it was an experiment, I only asked to backup my program files, 4.62 GB, and the target is a HI-MD minidisc. I only went through the first disc to see if it worked (it did) so that is a viable option. Now the question is, how many mc discs will I need to do a complete backup? My trial run confirms that my standard 80minute disc holds about 290 MB (the more expensive HI-MD discs hold 963 MB, but that might be the way to go.)
So my question is, can anyone give me an estimate of what the various kinds of compression will do as to size? (Not heavily into mp3s or visuals, so not that much already compressed.)
My hard disc right now has 28 GB. I'm willing to settle for the slowness of high compression.
Any estimates?
I will check in here as much as possible, but is it kosher to invite email responses? to Edit: e-mail address removed because of the security reasons

Thanks in advance.

 

I don’t think anyone could really give a very accurate estimation; it’s too dependent on the data being backed up. If you have the free space, you can just create an image on the drive itself and see how big it is. It is not recommended that you store the image on the source drive (and you will get a warning), but this would just be to check the image size.

 

Thanks. I did that and now am ok. Thanks.