This computer will be used to get my wife on the internet so she can chat with her friends.
Should I uninstall Xandros or format the HDD? Then should I install PCLOS after wiping all the old info and files?
We still don't know exactly what you did, as we have no details, so I would say yes, start totally fresh. Then, if you have problems take notes if necessary to tell us step by step what you did, what you expected, what you actually got, and if anything, what you've tried to remedy the situation.