i am getting a lot of 2019 errors on my windows SP6 server.  Also getting 2000 and 3001.

2019 - SRV - The server was unable to allocate from the system nonpaged pool because the pool was empty windows nt

2000 - SRV - The server's call to a system service failed unexpectedly

23001 - RDR - The redirector was unable to allocate memory

I understand that this could be a memory leak but am confused to why it is happening now since nothing has changed in terms of hardware or software.  It is causing the server to hang and now to reboot unexpectedly.

Obviously I am not expecting all in 1 solution (that would be be great though :)  but wondering how to begin my diagnosis?  I am familiar with perfmon but not sure what counters to use.

Thanks

Usually, I would start off with checking the Task Manager to see what your memory hogs are.  In most cases though these errors occur because of too little memory and/or pagefile size
As a stopgap measure try increasing the size of your pagefile first and monitor over the next few days.  Hope this helps.

Its got 512 MB of RAM and I have made it to 600 MB and am monitoring the NP Pool and Handles column within Task manager from what I read from another site.

If it's got 512MB of RAM then ensure that your pagefile is at minimum 1024MB (min/max)