85N02 apparently - not 58N02
eg
   http://www.onsemi.com/pub_link/Collateral/NTD85N02R-D.PDF

NB Chipdocs are generally useless for most people - being a paid service for
datasheets when many sites offer them for free.
I usually start with Digikey as a great datasheet resource.
eg
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=NTD85N02RT4GOSTR-ND

This may not be your version - Digikey list a range.

If you can't see why they died then they MAY be OK with a direct replacement
but that's not certain. Probability cannot be estimated without more
information.Lean towards expecting them to have been killed by another
fault.

For testing, replacing them with parts on short wire leads mounted on a
stripboard or other means of heatsinking may allow testing if access room is
very tight. In some cases the extra lead length will not be tolerable due to
extra inductance etc but that's liable to not be the case. Having the
circuit diagram helps - probably unlikely to be easily available. What's the
board worth?

Hot air pencil reflow possibly your best bet. Others will give better advice
on that.

Measurement (scope best) on a working version if one can be found  will give
some idea of what drive is present and what they do.
Best guess is that it is likely than not to not be fixable without much work
and or more information.


             R


<http://www.onsemi.com/pub_link/Collateral/NTD85N02R-D.PDF>

On my biostar P35D2-a7 Motherboard 2 FET type (On Semi) 58N02G (
>
> http://www.chipdocs.com/datasheets/datasheet-pdf/ON-Semiconductor/NTD85N02.html
> )
> blew, apparently the first one evaporated its drain leg, and the second
> baked to death. I recall looking at the screen and the computer appeared to
> be still running when we noticed the smell and turned it off!
> I wonder what might cause this type of failure, and whats the probability
> that just replacing these transistors could fix the problem?
> There is also a third different FET in that group
> http://www.alldatasheet.com/view.jsp?Searchword=FDD8780 which looks
> unharmed.
> I can see no nearby controller or gate driver!
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