I spend a fair bit of time trying out different icon size settings on my XP machine and so I thought I'd export the 'Shell Icon Size' key so I've effectively got hot-key access to different icon sizes. Anyway - I've produced a little zip file containing Reg files for the six main icon sizes, 32, 48, 64, 72, 96 and 128 pixels - just double-click to merge 'em with your registry and then log off and back on again. The reg tweak changes only the Shell Icon Size setting, open the files in Notepad to check it out if you're at all concerned. There are undoubtedly programs that can do this for you, but I reckon a double-click Reg file is far and away the simplest way of getting the icon size you want. Enjoy.
Download: XP Icon Size Registry Tweak Suite