My G4 Sawtooth running out of HD space

My internal HD on G4 has run out of space and I am not able to install any new software. I have an external HD and I am able to run the currently installed software on that. Could I install any new software directly on the external HD?

yes

with dmg installers just drag it onto the external hd and youll be set. with pkg installers just select the external drive is the volume to install on.

Thanks. It worked very well. If you could help me with the next step! My PhotoShop only runs on OS9.2 system I have. I also have OS10.4.4, so I installed PhotoShop on Classic Mode. The installation worked fine and the software runs perfectly from ext. HD. The problem I have is that I can only print when I disconnect the ext. HD. Since I don't have PhotoShop installed on the internal HD, I cannot print from the PS file copied onto the Desktop. I only have two ports—one for the printer and the other for the keyboard. The external HD, the printer and the keyboard are not compatible with the external Hub I had purchased. What would be the best strategy? Should I purchase PCI card? If yes, do you recommend 5-port or 2-port? And, how do you intall it?