same thing happening to me with vostro 260...did you ever get this fixed? Happens if computer sleeps or reboots, enable/disable card and it works. Thanks for the tip actually...would only work for boot splash screen and windows 7 screen, as soon as login screen appeared 2nd monitor would stop. I tried your enable/disable thing and voila!
Kind of late to this thread, but exact same problem with Vostro 260. HDMI output is fine through BIOS and Windows startup until login screen, then monitor goes to sleep. Windows proceeds as if VGA is only connected monitor. Disable and then re-enable Intel Graphics Adaptor restores HDMI output. This also occasionally happens when the computer has sat idle for several minutes (yet monitors are still on) and I move my wireless mouse. Tried many things, no avail.
The latest graphics driver for HD Graphics 3000 is version 188.8.131.5232; support for multi-monitor has been included.
Make sure you have loaded the latest one at:
Also, check if the video cable connections are fine, in other words, based on the computer specifications, you need to use VGA to VGA cable and HDMI to HDMI cables.
I do have the latest driver 184.108.40.20632. My problem relates to a signalling problem and HDCP. I have two identical Dell E2311H displays, one connected via VGA cable to the VGA port on the computer, and the other connected by a HDMI to DVI cable to the HDMI port on the computer. When you first boot the computer, you get the BIOS display and Windows startup screen on both monitors. When Windows loads the Intel Driver, the display connected to through the HDMI to DVI cable goes to power save mode. This appears to be because the HDCP negotiation fails while the driver is being loaded. If you disable and re-enable the Intel HD 3000 Display device, it works fine. These symptoms can be recreated by jiggling the DVI connector on the back of the monitor. Also, I had a Microsoft wireless mouse receiver plugged into the USB port next to the DVI port on the motherboard. Whenever I used the mouse after it had gone into standby, the initial wakeup signal to the receiver cause the same problem. Moving the Microsoft wireless mouse receiver to the front of the computer alleviated this. My speculation is that jiggling the cable, interference from the wireless mouse dongle, or change to the power state of the monitor -- anything that interferes with the signal to the DVI-based monitor screws up the HDCP negotiation, and causes the DVI-based monitor to go black, requiring disabling and re-enabling of the display device to recover. It is not just the driver, but probably a combination of the driver with the monitor and the HDMI to DVI cable that causes my symptoms. Regardless, still annoying, but I am living with it.