All that is relevant is the total amount of RAM your machine has. The most likely reason for your problem is because ECX is using up all of it.
Im thinking of win95-XP (i avoid Vista like the plague) - when you right click on My Computer, and click properties, you should go to something like:
What confuses me though is, these are my machines specs but I ran RC2 with no errors. Thats why I think you might have a cluttered computer, having lots or unnecessary progs running in the background, or you havent installed ECX correctly.
To uninstall ECX you must uninstalll everything and start again Im afraid.
Backup any custom stuff youve added you want to keep in a new folder
Uninstall ESF.
Delete any leftover files.
Reinstall ESF 1.2.x
Install ECX:RC2
Install Big Pack 8.4
Copy whatever stuffed you backed up back where it started.