One problem you mentioned is not a G2 problem at all... but a symptom of another problem,
which may actually be the root of all your issues with G2. No promises though... just fix it and see.

If you ever have a game ask you to insert a CD into drive X:, where "X" is a drive that doesn't
exist... then you need to do a clean uninstall... and possibly a thorough search of your registry
to remove all related registry keys. This happens when, say... you had more drives or partitions
when you originally installed, than you do now. Either that, or you reassigned the drive to another
letter after the install. It could also be that something/someone has mucked with your registry.

Don't take offense, if you're "legal"... but the only other possibility is that it's a pirated version
to begin with, copied from another machine... and the copyright protection routines are busting you.

Anyhow... once all traces of the product are removed from your machine, (double check!)
do a nice clean install of the product, and your troubles should be over. (Until such time as you
add/remove/reassign CD/DVD/HD drives again. Then you might need to repeat the process.)

Of course, you could also just search the registry, find which key(s) G2 uses to store the installation
drive letter... and manually change it right there. It would save a bit of work, no doubt.

Just some thoughts.