This article addresses the following issues:
V1 reports "Unable to open video" when selecting a file created by an external device (eg. hard disk based camcorder)
V1 displays a blank screen but slider controls appear to be working
V1 Professional basically 'does nothing' when asked to open a file
For users running Windows XP and Windows Vista:
1) Download and install the 'codec pack' to add a decoder to your system
K-Lite Codec Pack:
During the codec pack installation, do not change any of the default settings.
These codec packs cover the most commonly seen formats which require a 3rd party decoder (MPEG-4, H.264, AVC/AVCHD, DiVX/XViD)
For users running Windows 7:
1) Download and install the codec pack linked above.
2) After install find the K-Lite Codec Pack folder in your Windows Start menu under Programs or All Programs, under Configuration select ffdshow video decoder. Find MPEG2 in the list. Click where it says Disabled and set to libavcodec or libmpeg2 (both work fine) then click Apply and OK
3) Again in the Windows Start Menu under Programs or All Programs, find the K-Lite Codec Pack Folder. Under Tools select Win7DSfiltertweak. Click Preferred decoders
In the "32 bit decoders" section, find and change the default decoder for H.264, DIVX, XVID, MP4V and MPEG-2 from "Microsoft" to "ffdshow"