im going to bet you are having a drive issue
Personally this sounds to me like you are having hard drive failure.
the machine you are currently using...... was it a referb?
Have you installed tons of things on it, but havent really removed the programs your are not really using anyway?
Was this machine EVER infected by a bug that you removed?
If any two of those answers are YES..... im still going to bet, your drive is failing
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