Linux (particularly on a netbook) is not designed to run Windows programs. There are Linux alternatives for most Windows applications. If you provide details of his favourite software, I am sure we will be able to advise on the equivalent software.
AVG will not run on Linpus but it is usually to run Linux systems without antivirus software. By Yahoo, do you mean an instant messenger? Pidgin is a good linux equivalent.
To install additional software you need to enable advanced mode. Details for enabling advanced mode and other Acer one tweaks can be found here: click here