Registry problem and opening .eml file

I have been unable to open a .eml file. A search suggested that a registry scan (and repair) would solve the problem and that Reg Servo was the tool to use. The scan indicated (an amazing) 3000+ errors.
However, before registering. I checked on-line and Tech Guy advice seemed to be avoid at all costs.
So, I'm left with two problems viz repairing my system, if it needs it, and opening the .eml file.
Any help or advice would be appreciated.
Dave H