Request your school to upgrade to 2009. That is the only solution. 2008 cannot open 2009 files. Neutral format (which it sounds like you've already tried) is the only partial workaround.
Thank you for the answer.
In fact I tried a neutral format but it only worked partially as I've lost all the information concerning the assembly.
I'll try to rebuild it again (the assembly) on version 2008 and then work on it.
Thanks anyway once again
SW is not forward compatible. I.e. Future version files can not be opened using older version because of the functionality changes.
You will either need to request your school to upgrade to 2009 version or you will need to get files created using 2008 version.
Importing > Exporting files using netral format looses all the feature related information.
You may check with your school and get a student design kit if you are eligible: