My development machine has multiple drives and network drives. The C:/ drive is the oldest, slowest and fullest. I am using Elements, but have used Premiere over the years. Back then, we could make the program work better by off-loading files from C:. I do not see how to do so with P Elements 9.
Go to Edit>Preferences and change the location of the program's Scratch Disks.
I use a lot of FW-800 externals, to migrate my Projects between computers, and keep my full set of Scratch Disks on that external.
I would NOT choose one of the networked drives, because of speed.