Reset the system:

Unplug, remove (or if internal, remove the base cover and disconnect the battery from the system board), and hold the power button for 30 sec.

Reconnect the battery and try again.  If you still hear seven beeps, it's either a CPU or mainboard failure (on most systems built in the last 7-10 years, the CPU is soldered so the system board will need to be replaced).

If you require further information, post the system model number (i.e., Inspiron 5579, 5321, etc.).

It's still the same

The mainboard needs to be replaced.  Again, if you need a part or manual reference, you'll need to supply the full system model number.

If the system is under warranty, call Dell -- they'll repair it under warranty as long as there is no evidence of accidental damage.

I've been able to get it to work. Thanks a lot