Copy and Paste don't work

When installing a lan card under windows 95 on two quite different machines, they both have the same problems:
1. The "Paste" and "Copy" functions do not work (I'm not sure about "Paste" because there is nothing to copy :-) )
2. In Microsoft Word(MSOffice 7 and MSOffice 97 on the both of the machines) when opening a document it gives "Word cannot register the document" error. Sometimes it gives "Not enough memory to complete operation".

Would please someone advise me how to solve the problem without deleting and reinstalling Windows (this will works for sure, i've tried it, but I can't)?