We use a lot of Digital imagery and find the CD burner invaluable for making backups and sharing data. As for equipment, buy as much memory as the machine will hold. Win NT, unlike Win95, will utilize as much memory as can be stuffed in. The size of the hard drive depends on network space and file size worked with, anything around 6.4 should do you well. Drive prices fall quickly, so more can be added later cheaper than it would have cost you up front.
Programs usually dictate the processor.
I would get the fastest one possibe. Really anything above 300 will give you the performace eqivilent to most UNIX systems out there. This even covers our remote areas in Texas. Almost everyone recommended switching to NT, but keeping a machine in Win95 or dual boot Win95 and WinNT for troubleshooting installation problems, allowing you to rule out operating systems as the cause of a product that isn't working. Home software, particularly games, is least NT supported, business software is best supported.