Sony Ericsson Xperia X1 not recognised by PC's Windows 7 64 bit

Hello,
Connected to my Old Windows XP PC my Sony Ericsson Xperia X1 smart phone could be sync'd with ActiveSync and XP's Explorer used
to show it as a drive and I could transfer files/folders back and forth between the PC and the smart phone..

I got a new Dell Alienware Aurora ALX Desktop PC with Windows 7 Ultimate 64 bit.

Microsoft's Windows 7 Compatiblility Centre says Sony Ericsson Xperia X1 is Compatible -

I have the problem of Sony Ericsson Xperia X1 not being recognised by my new Dell Alienware Aurora ALX Desktop PC's Windows 7 Ultimate 64 bit - I get only an Error Window popping up from the systray and saying that USB Device is not Recognised - the device has malfunctioned and Windows does not recognise it - I clicked on the Error Window's button which gave me another
Window with the caption "USB Device Not Recognised" - malfunction - Unknown Device -Try again and if it doesn.t work - change the device!
The Dell PC's USB ports are all OK as shown inside Device Manager and they all work well with other USB devices like Pen Drives,
External USB FDD, External USB HDD etc.,

Sony Ericsson Xperia X1 is working fine in all other respects including Wireless Network connectivity. So this fault is not in the device.

Windows 7 Ultimate 64 bit does not install MS ActiveSync downloaded from MS.

I looked in the net for Windows 7 64 bit drivers for Sony Ericsson Xperia but found only some firmware like Sony Ericsson XPERIA X1 Firmware (NL) v.R2AA011 - I dunno whethersuch firmware are safe to use - I also dunno how to use them after downloading.

With the device connected I restarted the PC hoping Windows will install the smart phone automatically - no use!

Pls help!