how can you open a dll?

I'm not sure what you mean by "open," but this may help:

http://www.easydesksoftware.com/dll.htm

Depending upon your OS, a right click may offer ?Quick View?. This can
be useful if the data means anything to you. Alternatively, if you
open with ?Notepad? (or ?WordPad?) there is often uncoded manufacturer
data which can be useful for determining if it is relevant to your
system or simply junk DNA.

Best

normally, *.dll files (dynamic link library) are binary/compiled
files. So... opening them will just display junk unless you can read
machine code. Rather than opening .dll files, programs call/use
functions from them.

is there anyway to see exactly what is in a DLL?
When I open using notepad is is all in greek

Maybe you can tell us what you think there could be or what you are
searching for in the dll file.

the dll file is for a stock trading system. I want to see if the
system is genuine and the function in in the dll.

If you follow my suggestions you might be able to find the
information. The ?greek? you see is compiled code and would have to be
reverse engineered to render anything meaningful. Highly not
recommended :-)

However, as I said, there is often uncoded data at the end which can
be read. Disreputable DLLs rarely include software manufacturer
details, but it?s not a guarantee one way or the other.

Another little trick is to list your files by date and see what
matches up with the DLL. Again, this is not a guaranteed technique but
often alludes to the heritage.

Finally, there are techniques for determining which DLLs (etc) are
being accessed at any particular time but that?s getting a little bit
down and dirty.

Best

How hard would it be to reverse engineered? Do people do this sort of thing?

the only thing that is readable is below

This is a Win32 program
äu
òëè?ÀxøÃP?Ð?;ÂXuîé

Decompiling has varying degrees of success, depending in part on the
language used. Not good enough to extract the source code from Windows
though -- unless someone knows better. Generally it is illegal, as
covered by the license agreement. Not easy anyway.

This is a Win32 program
äu ò ëè?ÀxøÃP?Ð?;ÂXuîé

Not very informative, is it. I would have my suspicions. Try the date
match thing -- enabling ?view all extensions? and ?hidden files? first
and see if there is an ?exe? file of the same date. The other thing
you might try is search for ?files containing text? with say ?ÂXuîé?
as the text to be found. What by the way is the full name of the DLL.
Perhaps that can be tracked down.

Best

Your best bet is to make sure the dll is registered properly with your
OS (by using REGSVR32 at the command line) and then opening up Visual
Basic. You can start a new project then go to Project >> References
and select your DLL to add it to your project. If you then open up
your object browser (hit F2 in Visual Basic) and select the DLL from
the top drop-down menu, all of its objects and related Subs,
Functions, Properties and Events will be visible.