Generally speaking, motherboards do a POST prior to boot. That is, Power On Self Test. The various beeps and/or lights signal what might be wrong , or if there is a problem with the mobo. Search your docs or the web for the service manual and determine:
- If the board passes. this would indicate a different issue.
- What part of the board has a problem
This sounds like maybe a disk or an optical disc drive problem. We really can't trust them past 5 years. In my world, an image would have been done with "dd" and that image could be "dded" back to the original or a new, larger disk. I'm not sure which back up method was used here. Windows, in general, has the ability to refresh from a manufacturer disk or the recovery partition. If that is intact. This "repair" install leaves your files and settings in place and refreshes the system files. "chkdsk /f /r" and sfc /scannow are commands that could come handy if you have an OS. You can buy the original OEM OS that shipped with your unit from Dell. You need your serial number and it can only be done once.
An option is to boot from a "KNOPPIX" USB stick or other "live" OS and see if the motherboard hangs.
One more thing, the simplest things first. Open the unit (use a guitar pick) and check for dust bunnies. This means good grounding (ESD kills) and NOT spinning the fans with canned air. They don't like that. The older the computer is the more likely the need for cleaning. Dust, dirt, fuzzes, and smoke can short stuff or change component parameters.
If you believe it is memory, pull one stick, test, try the other, test.
More study is required. Find your POST codes. Start there.
A reformat and fresh install is a drastic measure.
CompTIA A+ Certified, AAS in Information System Technology, Mechatronics Specialist, Electro-mechanical Designer, 40 years cussing computers.