Do I have a memory problem?

I've just bought a 512MB stick of memory to add to my existing 1 GB
stick. When I try to run Sisoft Sandra to run the Memory Bandwidth
Benchmark, I get an error message telling me that 'Windows is out of
memory or resources.' Thinking it may be just a problem with Sandra,
I ran System Information in Norton SystemWorks. When I had just the 1
GB stick of memory (which benchmarked fine), I got the following info:

Total Physical Memory: 1024 MB
Total Windows Memory: 3675 MB
Free: 3488 MB
Used: 187 MB

With 2 sticks totaling 1.5 GB of memory, I get the following:

Total Physical Memory: 1536 MB
Total Windows Memory: 603 MB
Free: 365 MB
Used: 238 MB

So Windows recognizes the full 1.5 GB, but why did the total Windows
memory drop so dramatically? And is this related to my 'Windows is
out of memory or resources' error message in Sandra? Do I have a
memory problem or is this just an insignificant reporting error?

I've removed and reinstalled the new stick several times and was able
to reproduce the above figures.

The memory I have is:

Module 1: OCZ DDR 3200 400 Mhz (1 GB)
Module 2: OCZ DDR 3200 400 Mhz (512 MB)

I'm running WinXP SP2.

Any feedback would be appreciated.

Thanks,
Bob