I'm looking for a quote - I think it was Bill Gates who said something
like " our biggest asset walks out the door every night" pertaining to
how critical people are to the organization and why retention is so
important

mkpg,
Could the quote be, ?An organisation's knowledge walks out of the door
every night - and it might never come back?.

If yes it has been attributed to Mr Kevin Abley of ?Cap Gemini?
(providers of Consulting, Technology and Outsourcing services (1)) at
the ?OR Society? (provides training, conferences, publications and
information to those working in Operational Research (2)) Conference
on Knowledge Management, London, November 26 1998.

The quote is actually a paraphrase of what was said (?your knowledge
walks out of the door every night, and you can only hope it walks back
in through the door the following morning? (3)) being incorporated
into an article title covering the conference (reporter or editor
looking for a catchy title?), published in the societies newsletter in
January 1999. Since then it has been cited in its present form.

As to any connection to Mr Gates (as your question suggests) none was
found but a referance site (almost a shrine) to his speechs & essays
can be found here:
http://www.microsoft.com/billgates/default.asp

References:
(1) http://www.capgemini.com/about/
(2) http://www.orsoc.org.uk
(3) http://www.orsoc.org.uk/about/topic/news/knowledge.htm

Kind regards,
gfmaster