OK - I read about PAE and DEP. If I understood correctly, my boot.ini file should have these:

/noexecute=alwayson /pae

Now the System properties says 3,00 GB, Physical Addess Extension.

However, the system still only sees 3,00 GB of RAM. I tried to add the /3GB switch as well, but at the last stage of Windows XP booting, the ATI CCC crashes the system (BSOD). What's wrong?

I also tried to optimize my page file; first I wanted to check its I/O by adding a counter to the Performance-> Counter logs. However, when trying to choose "Page file" as the performance object, I'm faced with a very strange thing: instead of the many object names list, I have numbers only (interes, like 1150 etc). Something went wrong with my system, or is there a fix for it?