seven beeps usually indicates a processor problem. It is very seldom that the processor actually fails, it is most likely a motherboard issue. We may get more specific if you let us know which Dell you have.
See if you can perform a Pre Boot System Assessment (PSA Diagnostic) by holding the “Fn” while rebooting the system. Keep holding "Fn” key until the diagnostic gets initiated.
You can also try this.
1. Remove main battery.
2. The rear plate for the system is held on by screws. Remove all screws and remove the plate.
3. With the battery compartment nearest to you in the top left corner you will see the CMOS battery.
4. Using a minimal amount of force and a flat tool, pry the battery gently from its seat (it is held on by sticky substance).
5. Unplug the battery from the motherboard by disconnecting the white connector.
6. Wait for two to five minutes and then reattach the battery cable and reseat the battery.
7. Replace the rear plate and the retaining screws and reseat the main battery.
8. Attach the AC adapter and power on the system.
9. If a 5 beep code is heard, switch off the system and restart it.
10. When the system restarts and completes POST successfully, browse to the Drivers and Download page
11. Download and install the latest BIOS Version.