**modem setup not working**?

i have a smartAx MT882 modem which im trying to install. The problem is, is that i get an error message:The DSL modem is currently installed must remove before setup..etc. I used to have a BT Voyager 105 adsl modem but have incorrectly uninstalled it.When i try to shred or delete it i get the following message:dslagent:access denied make sure disk not full or write protected or file not in use. Im now unable to use my broadband connection ,any ideas on how to delete the rogue file "dslagent"? my os is xp home edition.