If your Microsoft SBS 2003 R2 server is complaining of high memory usage errors, they are probably due to MS SQL instances running on the server.  To manually set the maximum memory for the SQL instances, following the steps below:

Right click on your taskbar and bring up the Task Manager.
Click on the Processes Tab.
Click on the Mem Usage category to sort by it, then click it again to bring the highest ones to the top.
If PID is not the second column in your view, click on view and select columns.
Put a check mark beside PID.
Click OK.
Note the PID of the offending SQL instance.

Now, go to a command prompt (Start-->run-->cmd-->enter) and type the following command:

tasklist /svc

Scroll back up until you see the PID in the list. To the right of the PID, will be the appropriate instance to go after.

If the SQL process name is MICROSOFT$SBSMonitoring, the instance name is SBSMonitoring

Now we proceed at the command line as follows:

osql -E -S SERVERNAME\INSTANCENAME
sp_configure 'show advanced options',1
reconfigure with override
go

You will get a message that the option has been changed from 0 to 1.

Now to set the max memory to 128MB, type the following:

sp_configure 'max server memory',128
reconfigure with override
go

You will then get a message indicating the maximum allowable memory for that instance has been changed from 2 GB to 128 MB.

The memory will be set to this maximum almost immediately and you can check this back in Task Manager.

Exit out of the osql command shell by typing:

exit [enter]

Done!

If you have mulitple SQL instances hogging memory (normally this is true), then simply repeat the steps above for each instance.

Your SBS server should now be humming along with plenty of free RAM to allow it to do what it was meant to.

Cheers,
Aaron

NB: Thanks to Philip Elder for his post http://blog.mpecsinc.ca/2007/02/sbs-2k3 ... stall.html