Deskpro EN motheboard query

I have a Compaq Deskpro EN (series PDP-115p) and would like to upgrade the RAM.

There are 3 64MB cards in it at the moment and I would like to know whether the motherboard will accept 512MB cards or whether I need to get separate 128MB cards or what my options are.

I don't know what motherboard is in it but the number on the machine is ENS/C733/10E/6/64 UK with serial number 8124FHGZ0K7Z.

The case is the size of 3 pizza boxes on top of each other. It has a Intel Celeron inside and wins Windows 2000. On the motherboard I found a sticker with the following information: SP# P336CBC9VLY32, DG# 010701-000 and another sticker with 700 REV 0L S25.

I have no idea if this is helpful but if anyone knows what I can upgrade to I would be most grateful. Many thanks.