I am having troubles uploading .wmv and its annoying!

Whenever someone uploads a .wmv movie then it will just convert to .wmv and not .flv as needed so it will not work..

Also, in some instances if .flv's are uploaded <taken from youtube> then it will just create a 0 byte file.

Please assist me with this issue as my host says its the script. They run lots of clipshare sites with no problems..

Thank you.