|If this is a 32 bit OS this is a normal situation and there is no solution. The issue is that there is a 4 GB physical address space. The major user of this space is RAM, but there are others, such as memory mapped hardware devices which must have priority. There simply isn't room for 4 GB RAM plus other things in a 4 GB space. Typically about 3.25 GB RAM will be usable but it can be less, in some cases much less. It all depends on the hardware. If RAM is being shared with the video display this figure will be further reduced.|
The only solution is to install a 64 bit OS. That means a clean install (not upgrade) of the OS plus all applications. There are other considerations as well. In most cases it isn't worth the trouble.