SCAM bigtime!  Those errors you saw are harmless and do not indicate a virus, malware or that your computer was going to crash.  Had you let him onto your computer, he would probably have caused it to malfunction to extort money from you to "fix" it. He would likely have installed malicious software that would send your logins, passwords, credit card numbers, bank info etc to him whenever your were online.  Microsoft has warnings about this scam on their website:

http://www.microsoft.com/en-gb/security/online-privacy/avoid-phone-scams.aspx