I have an Acer 5735 laptop. The external monitor port seems to have stopped working. It had worked fine. We have a second identical laptop and when I plug the monitor cable in it auto-detects the external monitor. This one does not detect anything and I can't switch to the external monitor via display properties settings. Any ideas for getting it working again? Thanks

If you have an external usb keyboard you can connect that and use that instead. Also you can buy replacement keyboards online Acer Aspire 5735 Keyboard eBay There are also tutorials on line on how install them. Its strange that it just stopped working maybe a short or a driver issue. Also in a pinch you can use the on screen keyboard program windows has build in.

Inverter and backlight are obviously working if the screen lights up, which, leaves the video cable.
One method is to remove the switch panel cover, starting from the sides and gently unsnapping it and then pressing down on the connector that fits on the motherboard, where the cable from the monitor goes. If gently and then firmly pressing the connector (wear rubber gloves to avoid static), gets the screen to power up with an image, place a bit of wadding over the connector, just enough to keep pressure on and refit switch panel.

If that fails I think you are looking at a new cable

Connect your laptop to an external monitor and I expect you will find it is displaying OK on the external screen.
Browse ebay for a replacement screen.

Try to connect your laptop to a external monitor/lcd screen if it will display this will prove that the problem might be on the flex cable from your lcd to the board or might be an inverter problem.

get orignal charger for acer aspire 5735 pc and then try again

If the video chip on the Aspire motherboard is OK then the image on the external monitor would be OK. If not then the video/motherboard is faulty.
To gain access to data on the hard disk, remove the hard disk and connect it to an USB hard drive adapter and plug it into a working computer's USB port. The computer will see this as an external hard drive.
Alternately -
You can put the hard drive in an USB hard drive adapter case and use it as an external USB hard drive.

Can you please share the Make and model of the Laptop?

Is it a BRAND NEW monitor? The only way to be SURE your VGA port is bad really, is to see if it does the same thing with a completely different monitor. What I'm getting at is it could be the monitor itself. Maybe the monitor has some kind of "sleep" mode set? (There is such a thing as brand new AND defective. It's not common, but it does happen.) See if you can get the manual for the monitor, and read up on the different applications this one has. Most monitors have multiple ways to hook up. On the other hand, if your VGA port IS defective, it's probably safer to send out for repairs than replace the port yourself, unless you happen to be an accomplished solderer/electrician.

Hope this helps.

Try reinstalling sound driver. if still the same issue try external speaker to check if they have same issue. if external speakers work fine that mean its not driver issue and problem with your notebook speakers replace them.

Good Luck