Most ISOs are between 650 to 700 MB if the entire CD is used. There are some CD'sthat can go up to 900 MB, but those are very, very, very rare and I can't think of anyone who has ever released anything using that capacity (possibly because by that point, the data is more prone to becoming corrupt?)
So...going with 700 MB iso images...
700 * 3 = 2100 MBs or roughly 2 gigs. Due take into account the crudeness of this equation.
Now, this is presuming they use all three CDs to their entirity (SP?).
So, you are set. Furthermore, it is NOT that hard to buy a new, 80 gig HDD. When I bought an EXTERNAL HDD back in the States, it was roughly 80 U.S.D. By now, things should be even cheaper, perhaps 60 U.S.D. I know I was able to snag a 40-gig notebook drive (a much smaller, thereby more expensive drive) for about 50 U.S.D. So, even if you are in desperate need for space, you can always go that option. And once you have burnt the album, you can still use that drive for a good couple of years, even using it from one computer to another...