sandro
Parallels Developers
Hi Mark, glad to listen you again 
So after addition second hard disk startup your new VM, wait until Win XP loaded and logon into it. Go to "My computer" and if you won't to see there your newly added hard disk as system volume then do follow:
1. Go to "Control Panel->Administrative tools->Computer management->Disks management"
2. Find there your second virtual harddisk (guest OS see it as physical drive) and map it to some likely you volume letter
After these actions you'll must to see new volume at "My computer" and will be able to do necessary changes on it. Good luck.
So after addition second hard disk startup your new VM, wait until Win XP loaded and logon into it. Go to "My computer" and if you won't to see there your newly added hard disk as system volume then do follow:
1. Go to "Control Panel->Administrative tools->Computer management->Disks management"
2. Find there your second virtual harddisk (guest OS see it as physical drive) and map it to some likely you volume letter
After these actions you'll must to see new volume at "My computer" and will be able to do necessary changes on it. Good luck.