The simplest way is to get imaging software like Norton (Symantec) Ghost and make a compressed image of the hard drive of each PC and store it on a separate hard drive which is large enough to keep all the images.
If your users are allowed to store their files on the local hard drive in their PC, instead of the server, the compressed images can become quite large. If all the data is stored on the servers and the image comprises of the operating system and the local applications, the image files may still be 1GB to 3GB.
Imaging saves a lot of work in case an individual PC develops a problem, because you can restore the earlier image of the hard drive and get the PC working quickly, beofre restoring the data, if the users store their files on the local drive, assuming that you have a backup system for local data. Therefore you should be able to justify getting someone with experience in imaging to develop the procedure for your environment and/or do the whole excercise.
Of course, if your IT environment already uses an SOE (Standard Operating Environment) which is based on an image which is ghosted to a new PC to get the operating system and at least the most common applications installed in 5 minutes (instead of 3 hours by conventional manual methods), you would just use a base image if you need to re-install a PC.
However, 75 computers may not quite justify the planning and implementation effort for a full SOE, especially if they consist of different brands and chipsets.
If this sounds too daunting, you need to check what went wrong in your previous computer moves. Maybe you should just do a dry rehearsal first with a couple of PCs and set up standard procedures for your crew.
Keep the move simple with the minimum of changes and do not attempt to revamp the whole IT architecture on the fly during the move but, if you absolutely have to use the opportunity, set up a small test system first, in time before the move.
If you are only worried about saving the local data from the hard drives, you could get a large external hard drive which connects through USB, for example Maxtor OneTouch with 200GB - 500GB capactity. You can install the software from a shared network drive. For small volumes of data you can just use a 1GB USB memory stick, back up and save the data to another PC without having to install any additional software, if your PCs run Windows XP.
