Sorry, Lowolf, but it is a valid switch for the 32 bit XP. Check out the Microsoft Knowledge Base to confirm. I have tried it and it does work. The amount of Windows memory available to Photoshop increases to 3gb. My posting was to hear back from anyone who had a poor experience with its' use.
I fought with this switch for about 2 days. I don't know if I just had fat fingers or I didn't type the syntax just right. I finally got it to take. I couldn't tell a difference though. I did run it for about 6 months with no problems. I just recently went to xp x64 since the drivers were finally available. Same system but did notice a little speed increase increase.