PAE mode is a kludge:
http://pacoup.com/2009/05/27/pae-vs-...t-you-to-know/
http://en.wikipedia.org/wiki/X86-64
http://www.linuxforums.org/forum/sla...pport-pae.html
If you need >> 4GB, you need a 64-bit CPU and a 64-bit OS.
64-bit is a COMMODITY. It makes no technical and no economic sense to stick with your current environment if there's any way at all for you to upgrade.
All things being equal, you're throwing time and money away by sticking with your obsolete environment.
PS:
To use PAE, you need a PAE kernel. Easy to come by...
PPS:
The reason "the OS is showing 3049 GB" (your original post) is that you're using an old kernel. Whatever you do, UPDATE YOUR KERNEL (if at all possible)!
PPS:
I understand it's difficult to retire "perfectly good hardware".
I also realize that it's often IMPOSSIBLE to do so. For very good reasons (like "our mission critical application won't RUN on anything but this obsolete platform).
But in general, hanging on to an obsolete system is simply the Wrong Thing. The technical phrase is:
"Penny wise, but Pound foolish"