DEP ?

Hallo boys and girls!
I've got a problem on a windows 2003 r2 machine: after installing it properly as a vm (in vmware-server-1.0.4) on hp d360g5 (64 bit) hardware sometimes it's not possible to install an application (e.g. odbc30.exe) - the install process seems not to start. DEP is checked: i had dep shut off in boot.ini, now i could define exceptions (everything without the positive result). but if i try to install e.g. Adobe Reader it succeeds...
please could anybody give some hints?
Thank you, folks
Jens