Error with TDA installation in "reading only" modus


I installed the TDA 2.5.1 in the normal installation. The required .NET 3.5 update was automatically downloaded and installed. Afterwards I uninstalled the TDA to reinstall it in the “reading only” version. Everything worked well until the following error was giving in the End of the installation (the installation ended but the program dose not start):

“The following error was encountered attempting to establish the current DB2 environment” The error massage showed also a path which the problem that not every thing of the path could be found:
“C:\Programm path…\IBM\SQLLIB\BIN\netf20\specific “

After a little research I found out that this path is just by the .NET 2.0 version.

Now my question:

How can it be that the TDA (normal installation) runs normally without this path and when I try to install it in the reading only version, it requires this path??? Did any one know about this problem?

Thank you for your help!