The Microsoft link below may be of some help.
Troubleshoot installing Intellipoint, IntelliType, or LifeCam software
http://support.microsoft.com/kb/953691
You can also check thru the links at the link below as many ithers have the same problem.
http://www.google.ca/search?hl=en&source=hp&q=IntelliPoint+6.3+software+won%27t+install&btnG=Google+Search&meta=&aq=f&oq=
Tufenuf
I just purchased a Microsoft Wireless 5000 mouse at Staples. I loaded the disk (IntelliPoint 6.3)that came with the mouse to upgrade my Intellipoint software so I could use all the features of this new mouse. The software starts to load, I select my mouse from a list, agree to the terms and then after starting to load the software, it stops and I get an Error Code 1603. I tried going online and to download from there...same thing.
I am running XP Ver 3. The mouse does work ok as it is replacing another Microsoft optical mouse but why buy a mouse with more features and not be able to utilize them. What can I do to update the software?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic