Try an external USB keyboard as well as test it in Windows Safe Mode or any Live OS CD. There are too many today to list here but I noted it long ago at http://tips.oncomputers.info/archives2004/0401/2004-Jan-11.htm

Today there are a number of Rescue CDs including free antivirus boot CDs and then if your PC is working well enough and you have saved what you can't lose, begin scanning with a little help from Grif at link to follow.
Bob

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