No Modem Drivers
My neighbour has exactly the same problem
I downloaded the latest Speedtouch drivers (v3.01) from the website for him, but when we installed it, the device manager keeps refreshing and disconnecting the modem.
When i re-checked the website it said if you're upgrading from XP to Vista, the drivers will work, but if you're installing on a new machine, you'll have to wait until March 07 for the new drivers - There are 3 weeks of March left to go, so just wait for it.
My neighbour is ditching the modem (supplied by Tesco) and is going for a new account with Tiscali (using the CD provided by Dell in partnership with Tiscali - hopefully they're providing different modems now)