A few employees at my company are running low on disk space and do not wish to upgrade their whole computers (even though they are a few years old) so I have gone out an purchased some hard drives to keep them happy and with ample space.

I was wondering what is the best/quickest method to moving all their data/programs/etc over to the new hard drives. Is there a program I should go out and buy or maybe one you guys know of that works better than the rest. I want to get these guys back to work asap with minimal downtime.

Thanks in advance for the help and opinions.