Where are my phone contacts backed up in Windows 7?

I think that it depends, but in my PC I found them in C:\Users\[USERNAME]\AppData\Local\Broadcom\Bluetooth Software\BluetoothDeviceBackups\[DEVICE NAME]-[YYYYMMDD]-[HHmm]\pb .
They are stored as  .VCF.

I found this folder by searching all computer for device name (src).