One investment you can probably make yearly, or every two years (depending really on how much electronic files you accummulate) is extra memory.
I know that MyBook offers this in terrabytes, but that might not be a wise move also since if that hard disk becomes compromised in any way, you'd have lost all your files. Be vigilant in backing-up your files and deleting unwanted ones. Where applicable, have separate hard disks for your pictures (which are the must-saves for me!), music/video, programs, etc. If you digiscrap, have a separate disk for your kits for that too. Trust me, you can never be OC enough about this especially when everything we are and do are stored in gadgets (computers or celphones).
For realy important files (like PIN numbers, policy numbers, etc.), have them all stored in a separate memory stick.