Hi Nermin....... welcome to the vista forum
the problem you have is the 32bit OS, by default a 32bit OS has only 4gb available address space, this includes your VRAM (RAM attached to your GFX card) & other BIOS functions...
there is no way round this...... you will only EVER be able to utilize about 3-3.2gb, in order to utilize the full 4gb + you will need to migrate to a 64bit OS...
SK