There's some good advice here, and then there is....hmmm
The absolutely first thing you want to do is to turn off the computer. Then unplug the power cord. Then push the power(on off switch) switch in for about 5 seconds. This is to release the residual power which may be stored in the capacitors, etc.
Another thing. Don't spray the insides with regular canned air. Make sure it's specially made for computers and electronics. Regular canned air can produce static electricity which can ruin your computer.
If your Dell is an Optiplex model, it may be covered by a lifetime tech support warranty.
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