Three beeps generally means a bad block of memory in a chip (usually the first module). Try running with just one module and see if there is a change. If that does not work, run with the minimum for getting into the BIOS: CPU, one RAM module, graphics card (or onboard if it is available), a monitor, keyboard, and mouse (if your BIOS requires a mouse, otherwise, the keyboard is enough). Obviously, you will need the motherboard too.
My guess is, if the above still does not allow you to get into the BIOS, there is something else at work here; likely a motherboard or PSU issue. As you add and remove hardware, follow these steps for ESD safety:
- Shut down and turn off your computer.
- Unplug all power supplies to the computer (AC Power then battery for laptops, AC power for desktops)
- Hold down the power button for 30 seconds to close the circuit and ensure all power drains from components.
- Make sure you are grounded by using proper grounding techniques, i.e. work on an anti-static workbench, anti-static desk, or an anti-static pad. Hold something metallic while touching it to the anti-static surface, or use an anti-static wristband to attach to the anti-static material while working.
Once these steps have been followed, it is safe to remove and replace components within your computer.