Usually a hardware upgrade isn't required for a new operating system. Yet if you are planning to upgrade Microsoft Windows XP to Microsoft Windows Vista, it's almost impossible to avoid a PC overhaul.
Aside from things like the speed of your processor (minimum 800MHz), and using a videocard that supports Vista's sublime Aeroglass graphical interface (DirectX 9), the most important and limiting factor is going to be memory. If the PC doesn't have enough RAM to satisfy Vista's intense thirst, you'll be the slowest thing on two wheels. For the record, Vista's minimum memory requirement is 512MB, though realistically that should be doubled.
Much of the focus on Microsoft Windows Vista has revolved around its steep graphical interface requirements. Vista craves graphics cards that are DirectX 9.0C compatible with 128MB of memory to run its AeroGlass feature. Next is the large drive space requirement, sitting at 15GB just for its installation files, Vista is a fat OS.
Microsoft, Windows Vista, Memory, RAM, DRAM, System Upgrade