Can your old PC run Windows Vista? The answer is a definite “maybe.” Processor- and memory-wise, most mid- to high-end PCs sold in the past few years will probably do the job. But unless your PC has a modern 3D video card, it might not be capable of displaying the new Aero glass interface. If your video card isn’t up to snuff, you’ll be limited to the Aero basic interface — which looks better than Windows XP does, but doesn’t offer all the neat translucent 3D effects.
Here are the basic hardware requirements to run Vista:
Microsoft says that your PC must have a “modern CPU.” For the Home Basic edition, that translates into a 32-bit or 64-bit microprocessor running at a minimum of 800MHz; for all other editions, you’ll need at least a 1GHz microprocessor.
The more memory your PC has, the better. To run the Home Basic edition, you’ll need at least 512MB RAM; for all other editions, go with a minimum of 1GB of memory.
You need at least a 20GB hard drive with 15GB of free space to run Windows Vista Home Basic. For all other editions, Microsoft recommends a minimum 40GB hard drive. Obviously, you need a much larger hard disk if you want to install additional applications and store a fair number of files.
Windows Vista Home Basic needs your PC to have a CD-ROM drive. (Read-only is fine.) All other editions need a CD/DVD drive. (Again, read-only is fine.)
To display Vista’s basic interface, you’ll need a 3D video card that’s compatible with DirectX 9. To display the Aero interface, your PC’s video card must support DirectX 9 with Pixel Shader 2, have a minimum of 128MB graphics memory, and offer 32 bits per pixel, Windows Display Driver Model (WDDM) support. (To display the Aero interface, your PC must be running Windows Vista Home Premium, Ultimate, Business, or Enterprise editions; you can’t display the Aero interface if you’re running Windows Vista Home Basic.).
If your PC doesn’t meet any of these requirements, you can either keep using Windows XP or upgrade the components necessary to run Vista.
source: aol.com