If you first open the Excel application and then from the application try:

File > Open...

what happens??

You'll want to check a few things to see if the file really opened.

I use this:
Try to open the file
hit alt-f11 to see the VBE (where macros live)
hit ctrl-r to see the project explorer (like windows explorer)
Do you see your workbook's project in that window?
You should see something like:
VBAProject (Yourworkbooknamehere.xls)

If you don't see that, then your workbook did not open.

If you do see this, then close the VBE and go back to excel.

Try:
Window|arrange|Tiled
(Maybe the worksheet window is just off the visible screen)

If that worked, then resize the window the way you like.  (This can be caused by
the file being opened and saved by users with different display resolutions --
laptops especially!)

If that didn't work, maybe the workbook is opened, but hidden.
Try Window|Unhide
If you see the name of the workbook there, select it to unhide it.

====
If the workbook didn't open (when you checked in the VBE), I'd try this:

Close excel
start windows in safe mode
Windows start button|run
excel /safe
File|Open yourfilenamehere.xls

If it opens ok here, maybe you have a macro that's disturbing the opening of the
file.  Opening excel in safe mode will stop that macro.

Chip Pearson has some notes on how to diagnose startup errors:
http://www.cpearson.com/excel/StartupErrors.htm

And Jan Karel Pieterse has more notes:
http://www.jkp-ads.com/Articles/StartupProblems.asp