Haven't been able to auto mount a portable device for some time now. Here's what you do, and this is assuming you have the android sdk complete with tools on your system as well.
-Usbdeview (find it, use it, love it)
-Uninstall all htc and android labeled devices (disconnect device/s first)
-Connect device
-Start/right-click on computer
-Device manager
-You'll see android phone with the unknown image next to it.
-Right-click it, update driver
-Let me choose/browse the preconfigured ones.
-You'll see android phone and adb something something in the list, click adb something something
-Select the qualcomm ADB composite ... one and select ok and your good to go.
If you're having problems mounting sd to pc do the same thing EXCEPT
-You'll see android phone and adb something something in the list, scroll all the way down and select universal serial bus controllers
-left column, select compatible usb device
-right column, select mass storage device and select ok
-mount sd card as usual...
When I get to my pc, I'll clean up the how to (remove the something something's along with the ...'s and replace with correct ... directories)