Yes, you can.
No.
1 GB recommended
If it has the minimum RAM and hard drive space, you can.
two
If you are asking if you can run Windows Vista on 256 MB of RAM, then yes. However, the Windows installer will not allow you to install on 256 MB of RAM without a patch. If you are asking if you can use Vista on a computer using 256 MB memory modules, then yes.
Assuming they are the same type, e.g. DDR2, yes you can. RAM doesn't rely on the OS to work, as it is hardware, not software. You can't, however, put laptop RAM into a desktop system.
Windows Vista will run on a computer with a minimum of 512 MB of RAM
For Windows Vista to run optimally, you should have at least 2GB of RAM; however it will run with 1GB,
You can only install 64 bit Windows Vista on a machine with 4GB ram. If you have enough ram then you need to do a clean install. To do this boot up your machine with the 64 bit Vista CD. Then follow the on screen instructions.
Suposing that your computer does not have a propietary bios link such as Hewlett Packard, Acer etc, but does have a 1 GHz processor or faster, 512MG of RAM for Vista Home Basic or 1 GB RAM for Vista Home Premium then you can install Vista. If you have a valid copy of Windows XP complete with keycode you can purchase the Vista upgrade. If not you have to purchase the full version in which case you may as well go buy a new computer.
You can, it is possible, but i wouldn't, you probably wont enjoy the user experience.
There are many reasons The main on is your computer does not pass the basic minimum standard .For example xp needs a computer with 128MB ram and vista needs 512 MB Ram