[X-Newbies] Error advice

[Keith Mills]

Bonjour everybody

I am currently using  OS 10.3.3. When I bought this model the 
shop/Apple agents transferred my existing personal and business data 
onto the new machine for me. Mostly it works all right, but I cannot 
open some of the files.

I get the message: An I/O error occurred.

What does this mean? And is there anything that I can do?

Many thanks (as always) for any advice.

Keith Mills