3GB limit in XP? Go to Microsoft’s websites to find something else.
This shows the limit of the 32bit versions at 4GB.
You can also do some 4-Gigabyte Tuning to utilize all 4GB of memory.
Memory Support and Windows Operating Systems
Operating Systems and PAE Support
Physical Address Extension - PAE Memory and Windows
Upgrading Memory Beyond Three Gigabytes (3GB) in Windows XP
TCC Shelbyville blog: