Can not upload file while it is used by another process

Hi there,

I am using the standard fileupload server tool in asp.net 2.0 to upload
files to my server. Everything works perfectly until I figured out that
certain files (under 4MB) gave me an error like it happens when you
upload files greater then 4MB. This happend to files with a size of
200kb.

After 10 hours of intense brainwork, I figured out that when a file is
locked by windows xp, any attempt to upload this file, which size ever,
give me this error. In my case I tried to upload the BACKUP.PST file.
This never worked because Outlook 2003 was opened on my system and
locked it. As soon I closed Outlook, no problem to upload.

Is there anything I can do to
1) upload a protected file (I dont have any access to my customers
machine)
2) intercept somewhere, somehow and give the customer a proper error
message

Thanks for helping

Mike