Out of memory error

I do get an out of memory error after opening my computer. First this occurred in win95 and continued to occurr after upgrading to win 98. I upgaded my memory to first 128 meg and then 256 meg of sdram. I still get this error only after opening my computer on the desktop. I can close everything that is open and still the error does not go away. It will persistantly calim I have no memory to run any more programs. it will also cause an invalid link or link is unavailble when I click on an icon after the error occurs. So far the only way i can clear this error is to reboot. This is an annoying error. Anyone got any other solution????