I tried Peter's suggestion but it didn't work. The debug report now is:
Spoiler:
calibre 2.43 isfrozen: True is64bit: False
Windows-8-6.2.9200 Windows ('32bit', 'WindowsPE')
32bit process running on 64bit windows
('Windows', '8', '6.2.9200')
Python 2.7.9
Windows: ('8', '6.2.9200', '', 'Multiprocessor Free')
Successfully initialized third party plugins: DeDRM && Kindle and Mobipocket DeDRM && Ignoble Epub DeDRM && eReader PDB 2 PML && Inept PDF DeDRM && Inept Epub DeDRM && Quality Check && Generate Cover && Open With && Fantastic Fiction && Resize Cover && Barnes & Noble && View Manager && Search The Internet && Favourites Menu && Count Pages && EpubMerge && Find Duplicates && EpubSplit && Overdrive Link && Modify ePub && Reading List && Kobo Utilities && Manage Series && Overdrive Link
USB devices on system:
[u'usb\\root_hub30&vid1022&pid7812&rev0003',
u'usb\\root_hub&vid1022&pid7807&rev0011',
u'usb\\vid_045e&pid_0745&rev_0634&mi_00',
u'usb\\root_hub&vid1022&pid7807&rev0011',
u'usb\\vid_045e&pid_0745&rev_0634&mi_01',
u'usb\\root_hub20&vid1022&pid7808&rev0011',
u'usb\\vid_045e&pid_0745&rev_0634&mi_02',
u'usb\\vid_18d1&pid_4ee1&rev_0228',
u'usb\\vid_10f1&pid_1a43&rev_1212&mi_00',
u'usb\\vid_0930&pid_021d&rev_0200',
u'usb\\vid_045e&pid_0745&rev_0634',
u'usb\\vid_0bda&pid_0129&rev_3960',
u'usb\\vid_10f1&pid_1a43&rev_1212',
u'usb\\root_hub20&vid1022&pid7808&rev0011',
u'usb\\root_hub&vid1022&pid7809&rev0011']
Traceback (most recent call last):
File "site-packages\calibre\devices\scanner.py", line 85, in __call__
DriveError: No removable drives found
Drives detected:
No disabled plugins
Looking for devices of type: MTP_DEVICE
List of WPD PNP ids:
[u'\\\\?\\usb#vid_18d1&pid_4ee1#0ab62c85#{6ac27878-a6fa-4155-ba85-f98f491d4f33}']
MTP device: \\?\usb#vid_18d1&pid_4ee1#0ab62c85#{6ac27878-a6fa-4155-ba85-f98f491d4f33}
{'device_version': u'1.0',
'friendly_name': u'',
'has_bulk_properties': True,
'has_storage': True,
'manufacturer_name': u'asus',
'model_name': u'Nexus 7',
'protocol': u'MTP: 1.00',
'serial_number': u'0ab62c85',
'storage': [{'capacity': 13105287168L,
'capacity_objects': 0L,
'description': u'Internal storage',
'filesystem': u'Generic hierarchical',
'free_objects': 1073741824L,
'free_space': 9003773952L,
'id': u's10001',
'name': u'Internal storage',
'rw': True,
'type': u'fixed_ram'}],
'type': 'media player'}
Trying to open: \\?\usb#vid_18d1&pid_4ee1#0ab62c85#{6ac27878-a6fa-4155-ba85-f98f491d4f33}
Opened Nexus 7 successfully
Device info:
{'device_version': u'1.0',
'friendly_name': u'',
'has_bulk_properties': True,
'has_storage': True,
'manufacturer_name': u'asus',
'model_name': u'Nexus 7',
'protocol': u'MTP: 1.00',
'serial_number': u'0ab62c85',
'storage': [{'capacity': 13105287168L,
'capacity_objects': 0L,
'description': u'Internal storage',
'filesystem': u'Generic hierarchical',
'free_objects': 1073741824L,
'free_space': 9003773952L,
'id': u's10001',
'name': u'Internal storage',
'rw': True,
'type': u'fixed_ram'}],
'type': 'media player'}