Upgrading old machine

I was given an old HP Workstation, xw4300 - HP xw4300

It only has 1 gb of RAM & a pentium 4 3.00 ghz, and an old copy of XP.
I'm thinking that if I can add another gig of memory I can maybe put Win 7 on it & let my son use it for basic web surfing - but not sure if I can add RAM.

The specs say

Memory

Up to 8 GB of DDR2 533 MHz ECC (with 2 GB DIMM availability expected in July 2005); or
DDR2 667 MHz ECC (4 GB max.); or
DDR2 533 MHz non-ECC (1 GB max.)

I'm taking that to mean I can install up to 4 GB of DDR2 667 if its ECC & only 1 GB if its non-ECC - is that correct?

Looking at memory on NewEgg - some of the memory says 'ECC: no', the rest say nothing about ECC.
If a memory stick doesn't say 'ECC: no' does it mean it is ECC?

Is there any RAM I can use for this old box to get to 2 or 4 GB?

Any advice is appreciated -
Thanks
BT

All the indicators I can find point to this being a deliberate distinction by HP as to what memory configurations they preferred to supply rather than any actual requirement. It was more common in the past to specify ECC for large memory configurations:

http://h10010.www1.hp.com/wwpc/pscmisc/vac/us/en/sm/workstations/xw4300-faq.html#faq3

"The HP xw4300 uses DDR2-533 ECC memory technology for memory configurations above 4 GB."

"three types allows you to choose the memory speed and configuration that meets your price and performance needs."

Crucial offer 2GB Non-ECC DIMMs guaranteed compatible:

http://www.crucial.com/store/mpartspecs.aspx?mtbpoid=32073A77A5CA7304

which indicates they're certain it will be fine, which is what I would expect.

Thanks very much Platypus -
BT