I guess many people have faced this issue before, however I couldn't find a solution which solves my problem.
I successfully installed Arduino IDE 1.6.9 on Windows 7 Home Premium 32-bit.
I have several Arduino boards Unos and Megas. Whenever I connect them through a USB cable to the PC, it appears under Other Devices in Device Manager and shows a yellow triangle on the icon. Please note that I face the same issue with both types of arduino boards (Uno and Mega). My USB ports are working normally, as I can connect other USB devices with no issues.
I was searching in the forums for a solution, and several people seem could solve the issue by manually installing the drivers. I also tried all the possible solutions, but none of them helped.
Is there anyone who could solve this problem, please help!
Look at the markings on the chip near the USB connector - it'll probably say CH340G, 16u2, or FT232R on them.
Official ones use the 16u2 (and old official boards used FT232R)
The IDE includes drivers for the 16u2, and the FT232R. However, a lot of the clones use the CH340G serial adapter, which isn't included with the IDE - google will get you the drivers for the CH340G. It's called CH341SER or something - installer is engrishy as hell, but the CH340G's are cheap and reliable.
If it's an FT232R, and you bought it online last year, it could be a fake FT232R - there was a spell of counterfeit ones last year, and then FTDI updated their drivers so the fakes don't work. Google ftdigate for more info.
I tried to connect the same boards to another computer, and both of them are recognized by the OS normally.
If it would be a USB connector issue, then I guess they wouldn't work with any computer.
I think the problem is that you don't have drivers installed (which is consistent with your most recent post - if the other computer has the drivers installed), as I said in my previous post. In order to determine what drivers you need, you need to determine what kind of USB adapter chip the board you have uses - most "Arduino" boards are clones, not official ones, and the clones often use a different USB adapter (hence requiring different drivers).
So, to determine what to do next:
Look at the markings on the chip near the USB connector - it'll probably say CH340G, 16u2, or FT232R on them.
Each of these points in a different direction, so you need to determine this, otherwise we can't tell you what drivers you need or otherwise analyze the problem.