Just to clarify...... when the OP mentioned  XP SP3 bit, I was under the impression that he meant Windows XP home version, which is 32 bit also, and on that one the /3GB switch doesn't work. On Windows XP Pro 32 Bit the switch will work, but from what I did read the OP isn't talking about XP Pro at all, but about XP Home version. In the light of that, the info I gave is correct.

Quote - except the OP wasn't installing XP64.. but XP32 on which the /3gb will work on the Pro version (sorry home? never heard of it...)

You never heard of XP home?

Artwork and 3DToons items, create the perfect place for you toon and other figures!

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Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk