Judging from the descriptions of your symptoms, it is most likely not a software issue at all. It may be a hardware issue!
All modern keyboards are multiplexed. What this means is that the keys are wired in a way that only one can be read at a time, at a very rapid rate. This allows the manufactures to use less wiring, or traces in the keyboard assembly. Unfortunately for you if one of the traces are broken, many keys at one time fail. Depending on the proprietary configuration of the keyboards internal wiring, any given set of keys could cease functioning.
The only solution is to replace the keyboard assembly. However there is good news. Laptop keyboard assemblies rarely exceed $20 USD in cost on online auction sites. Use the service manual oldturkey03 linked you to in order to do a quality job.
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Did you get the Dell drivers for your machine?
crwdns2934271:0crwdnd2934271:0 oldturkey03 crwdne2934271:0
I had the same problem. Keys on left side were unresponsive. This SOLUTION worked: shut down the laptop. Pull out the battery. Wait a minute. Insert battery. Hold down power button as it starts for 10 seconds. Then release power button and let it finish starting up. All my keys worked properly after that.
crwdns2934271:0crwdnd2934271:0 chirchlady crwdne2934271:0