You got the wrong version then. TransferPlusSetup11RELEASE.exe is for MSN Messenger 7 and Msgplus 3. Go to Control Panel -> Add/Remove Software and remove the File Transfer Plus 1.1.
Then download the SCRIPT using this link:
http://www.filetransferplus.com/pre/FileTransferPlus060830.plsc
(NOTE: make sure you download it as an PLSC file. If you use Internet Explorer, it will suggest to download it as a zip file. If that happens select save as all files in the save dialog window and add .plsc to the file name)
