HELP - I can`t install Cognos 8 BI

[SafarXXL]

I need help with installation IBM Cognos 8 BI starter Edition.

I did everything by the "book" and still it doesn`t work - problem is that Cognos 8 BI Starter Edition contains database DB2 Express Edition and Websphere and between the installation DB2 show same errors about some "paths are invalid" but funny thing is that installation shows me that DB2 is installed and installation resumes installing.
When installation is complete everything is installed except DB2.

What should I do or what is that I am doing wrong?
Any ideas?

Thanks for help