I am using Excel 2010 and Windows 7 and I would like to make use of
some .dll files to experiment and get some experience making my code
moore protected in future projects. I also realize that Microsoft
doesn't sell this any moore and I know there are some issues with
classic Visual Basic running on Windows 7, but that there are tricks
too make classic visual basic work with Windows 7.

Now, I have one possibility to buy a good old classic Visual Basic
Professional edition to a very good price, but a have one question. Is
it legal to buy a used one? I can also buy a new one, but for a higher
price.
The last option is probably Visual Studio 2010 but that seems very
expensive to buy for only a few .dll or assemly files, if that is what
they are called. Somebody that have some comments or suggestions?

Regards
Jan T.