Agree with FBW, upgraded my Dell from 64mb with non-branded memory. Only ****** was it had 2x32mb dimms and wanted to go to 128mb but 64/32/32 was not a listed option so bought a 128 dimm which worked fine - then tried the old dimms anyway and they worked fine alongside so ended up with 192 (128+32+32). Vast improvement, especially in graphics handling eg big scanned picures etc.
'Dell' specific problems came later when I upgraded further - I needed to change the case as it had dell specific cables and front panels connectors which would not fit standard motherboards.