How are you trying to install them? Are you connecting the CD drive to the downloaded ISO?
Here's how I did Ubuntu Studio (which is no different than 7.10).
From the Virtual Machine Library:
1) Select New
2) Click Continue
3) In Operating System drop-down select Linux
4) From Version select Other 2.6 Kernel (unless you specifically downloaded the 64-bit version, then select 64-bit).
5) Click Continue
6) In the Save As - give it a name you want.
7) Where -- the location you want to store your VM
8) Click Continue
9) Virtual Hard Disk - I give mine 20 gigs, you can adjust up or down depending on your needs.
10) Click Continue
11) On the next screen I always uncheck the Start VM and install operating system now so I can adjust the other settings (memory and processors). But this is where you'd point to the downloaded ISO for your virtual CD drive or your physical CD if that's how you're doing it. Click Finish.
12) back at the VM library highlight the VM you just created and select Settings.
13) Click on Memory - I have 6 gigs of ram on my MacPro, so I give my VMs at least 1 gig. Adjust up or down, the default (256M) should work okay depending on what you plan to do with the VM. Click apply.
14) Click on processors - Unless you have a multiple core MacPro you may just want to leave this at one virtual processor. Apply any settings if you changed them.
Double-click or select run with the VM you just created highlighted and walk-through the guided install.
If you need to install the VMWare Tools, just search for "install VMWare tools on Ubuntu" on Google. You may have to apt-get some kernel headers and dev tools to be able to compile from the source.
Hope that helps. If not, please post specific questions and we can help you out.
