Sdram Computer Nonecc

Help upgrading memory?

I am upgrading a old compaq desktop that had 64mb sdram pc100 nonecc
I then added another 128mb sdram pc100 nonecc
I also added a 256mb sdram pc100 ecc
and when i turn on the computer it said 164-Memory Size Error
I went into windows and it said it had 192mb of memory so the 256mb ecc sdram was not showing
I restarted and did not get the error message but windows still showed only 192mb of memory? Whats wrong?

As it is an old computer, you are probably exceeding the amount the computer is compatible with.

For example, my old laptop could only use a maximum of 192 MB of memory.

It sounds like the same problem.