Dell dimension 3100 when turned on bleeps and no display on monitor

No bleeping sound? Then I would say that your RAM is no good.
If the coolers don't run I'm afraid that the processor is faulty.
Any more I cannot tell you right now, sorry.

Check your monitor cable first! Try reconnecting your display cable both at the computer and monitor ends. If it's still pink, try reinstalling the vga graphics driver from the Dell Utility CD-ROM (Or download from Dell's support site http://www.dell.com/support/home/us/en/19/product-support/product/dimension-3100/drivers then select you PC model's video driver and re-install it. if after re-installing the video driver your display's still pink, try connecting to a different monitor - if a different monitor displays correctly, then its your monitor that's faulty. If it's pink on a different monitor too, then it's your PC video hardware that's got the problem - At least you'll know whether it's the monitor that's faulty or whether it's your computer's graphics hardware. (if your computer's video chip is faulty, then I suspect you'll need a replacement motherboard - $$$ - as I think the video is "on-chip" on the Dimension 3100 - so it may be time to consign it to the scrapheap and buy a new system if you can afford to)

It would help if you'd mentioned the state of the system and diagnostic lights as well.

Here's a link to a dell troubleshooting page which should help you.

dell troubleshooting

HERE is the documentation straight from Dell. It gives the explanation of the beep codes and other diagnostic information like what the lights mean. It's the best place to start.

Do you mean you want to change the resolution? in control panel

The monitor is probably faulty. To determine if the monitor or the video card is faulty, connect a different monitor to your DELL. If the image is OK on the other monitor then the other CRT monitor is faulty. Repairs to the CRT monitor may not be a cost effective solution, I suggest you buy a LCD monitor.

Check to see if the monitor cable is connected properly.

You can purchase and aftermarket monitor. I bought a nice LCD from Wal-Mart for about 99 dollars. Also, tigerdirect.com sells refurbished and new monitors relatively cheap.

try to check the cable connection between the monitor and the tower. what is the color of the LED light on the monitor?

Speakers are not built into the box itself. They may be in the monitor, or completely separate.

Did you get this directly from Dell, or from a third party. Dell would have shipped you speakers with it, or a monitor with speakers built-in. Purchased from a third-party you might just get the box itself.

If you have a monitor with speakers, you still have to connect the sound output from the box to the monitor.