There's one little problem with going to 64 bit for him. He's using a version of Autocad that was designed for Win3.1 and Win95.
ding! ding! ding! ding! we have a winner!
My solution will be to convert to the DOS version (I have both DOS and Windows version) on a dedicated box - which will allow it sole control of the system, allowing me to go up to the max of 3.6GB RAM. 32-bit hardware maps a I/O into the 32-bit memory space, so even with 4GB of physical memory, only about 3.6GB can actually be accessed. Windows reserves an additional portion for the OS that applications cannot touch, so the practical ceiling for available memory to applications is 2GB, even if you force a larger swap-file, the 32-bit architecture will not permit addressing above that limit.
I could use a 64-bit environment, assuming I could run a 32-bit app in it (I have 64-bit XP available to me), allowing the application to take as much memory as it can handle - the literature for AutoCAD r13 says it can address 4GB of RAM, but I know at the time they published it, having more than 32MB
of RAM was unheard of; so I have my doubts as to the accuracy of their 4GB use claim. It will certainly run into the 32-bit address space limitations, but might still have the same 3.6GB ceiling - as in the 32-bit "sandbox" the I/O will be mapped into the 32-bit address space. Functionally, this leaves me with the best option (shy of upgrading to a newer version) being to run it on a dedicated 32-bit hardware platform with the maximum amount of addressable physical memory available.
I could go on and on and on about XP, Vista, and Windows 7. I will not be moving to either Vista or 7 anytime soon. Fedora is my OS of choice, and the only reason I still have a windows box around at all is for a few legacy apps such as AutoCAD. Eventually, I plan to learn Blender and do much more in that. I may try and see if I can run AutoCAD r13 under WINE, but I doubt the hardware dongle will work with WINE - it is a miracle it works with XP.