You don't need Asto File Manager (or any other app) to transfer files between your PC and phone. All you need is the USB cable. When you're connected, you'll see several options re connecting the USB on the phone's screen. Select Disk drive (mount as disk drive), then you'll be able to see the phone's SD card as a 'Removeable Disk' in Windows Explorer and transfer files like you would between any drives.
(If you prefer to transfer files manually, then you don't need to use HTC Sync at all, although you might find it useful to back-up contacts and calendar now and again.)
