I think you mean IIS.
IIS is not a sepprate download and will only run on Win2k, Win XP Pro, Win Sever 2003. If you have one of these OS's then you can install it from add and remove windows components in the control panel. If you don't have one of these OS's then I'm afraid you are out of luck.
If you do have Win XP Pro on your system you will need to get hold of the installation disk to install it.
I'm afarid though it is not available with the home edition of XP, although if you do a search on google there are a couple of registry hacks to force it to install on the home edition, but you will still need the disk.
Edited by -boRg-