Auto-connect Bluetooth headphones in Windows 7 64 bit

If you right click your volume/speaker icon by the clock and go to Playback Devices you could try setting them as the default playback device. That way, they should take over when they reconnect.

I'll admit, even with Windows 7 I find the connect/reconnect situation doesn't exactly go smoothly at all times. I liken it to docking/undocking your laptop. Most of the time it's pretty smooth. Occasionally not so much.

I've got a Logitech Bluetooth device, and I use a small quick-and-dirty AutoHotkey script to connect or disconnect. And I love it.

Save it as connect.ahk and adapt it to your needs. Look at the AutoHotkey documentation on how to do it. Since I've got a Lenovo Thinkpad I do not know if it works with your PC, but perhaps it may give you another idea how to solve it. Good luck!

;FHEM: Turn on Receiver Power Socket (You probably want to delete the following line!!)
;runWait, "curl.exe" "http://fhem.box:8083/fhem?cmd=set`%20music`%20on"

;Open control panel's BT device connect Window (Adapt the Address to your device specific one)
run, "C:\Program Files\ThinkPad\Bluetooth Software\BTWUIExt.exe"  /deviceAddr=c8844711xxxx

;*******************
;replace "(49)Logitech Adapter" in all following lines by the Window title depending on your device
;*******************
; Wait for the Window
WinWait, (49)Logitech Adapter,
IfWinNotActive, (49)Logitech Adapter, , WinActivate, (49)Logitech Adapter,
WinWaitActive, (49)Logitech Adapter,

;then click on "connect"/"disconnect" button (the window must be big enough to show the button), maybe you need to adapt the coordinates (?)
MouseClick, left,  778,  213
Sleep, 100

;close window
WinWait, (49)Logitech Adapter,
IfWinNotActive, (49)Logitech Adapter, , WinActivate, (49)Logitech Adapter,
WinWaitActive, (49)Logitech Adapter,
Sleep, 100
Send, {ALTDOWN}{F4}{ALTUP}