The one memory vendor that many use including me. Its listed on this link below for your XPS 400
Banchetto 101 Case-Less System
eVGA 780i Mobo
eVGA 295 GTX Video
8 Gb Corsair Memory
Thermaltake TRUE Black CPU Cooler
VelociRaptor 10,000 rpm HD
Windows 7 RC 7100
The 400 can take 4G, but with a 32-bit OS, you will only have 3G to 3.5G available.
thanks guys would you guys recomment this?