This will be a problem, as you should first image the disk(s) and work from the images, not the physical disk. It is especially important for the disk throwing errors, every read attempt may worsenit's condition. Use tools like (g)ddrescue to make a copy despite readerrors.
I know, and am able to understand the "why". Maybe ddrescue or another tool is able to build partial images? It would not be the panacea, but maybe a little better? Buying a HD of more than 1Tb (for (1), for (2) it would "only" be more than 500Gb ) is not really an idea I like, HD are not exactly what I name cheap.
Again, try (g)ddrescue first, and when you have a good image work from that, preserving the disk from further damages.
For the good disk where the partitions have been deleted, you can try to recover partitions with "testdisk", it is quite efficient and fairly easy to use even for someone not familiar with consoles. To recover the images, regardless of the partitions status, try "photorec", it does a very good job most of the time and it's interface is self explanatory.
Thanks for the hint. I'll try this today.
Teach your friend(s) to backup as a Christmas gift, he'll thank you for the rest of is life ! ;-) Tools like sbackup, backintime, luckybackup and the such are easy to use even for my mother (!) and efficient enough for single-computer personal use. Good luck.
Of course, but, you know people, they *usually* prefer to not worry until a problem comes. I'll take a look to your tools, hopefully one run on the most common OS, so they might be able to use it :)