For Word:
oWord = createobject("Word.Application")
with oWord
.Documents.Open(m.lcFile)
.Visible = .T.
endwith

You need to look at exactly what you need to do as most applications are different and have different object models.

What application are yoou wanting to open HTML and XML in?
You can also just use the RUN command to run applications.

So you cound open a TXT file in Notepad by:

run /N notepad "c:\tmp\dir1.txt"