Audhi203 has given you the link to the IIS 7 Management TOOL - not to IIS.
You CANNOT install IIS7 on 2003. IIS is an OS specific feature:
IIS 4 runs ONLY on NT 4
IIS 5 runs ONLY on 2000
IIS 6 runs ONLY on 2003
IIS 7 runs ONLY on 2008
IIS 7.5 runs ONLY on 2008 R2
