How to uninstall PAE Patch for XP?

I tried installing the "WinXP-PAE-Patch" and while it appeared to work, it causes my machine to BSOD with "IRQL_NOT_LESS_OR_EQUAL" after opening a few programs.
I have run Memtest6+ and it passed 2 passes with 0 errors, plus Windows 10 ran fine, albeit slowly, on this machine.
The problem I have is, without the PAE patch, Windows XP is only able to use 2.5GB of the 4GB RAM. Whereas the PAE Patch let me use all 3.75GB (as I have allocated to the X1200 in the BIOS).
Is there a way of uninstalling this patch? There is no documentation for this and I can't find the supposed backup.
I did try another PAE patch before this, and that kept causing a black screen instead of a BSOD.
Thanks!