Terman was a member of the US Army Signal Corps' advisory board at the time, and when asked by the army how best to acquire a computer for research purposes, he naturally turned to Hewlett — one of his former students — for assistance. Unfortunately, HP were then immersed in the world of electronic test equipment and, as such, had very little knowledge of a product from which they would eventually make huge profits; hence this reply. 10 years later, they introduced one of the world's first 16-bit minicomputers: the HP-2116A.
Transcript follows. Image courtesy of Steve Blank. Many thanks to Mac Harwood for suggesting it.

Image: Steve Blank
Transcript
HEWLETT-PACKARD COMPANY
June 13, 1956
Dr. F. E. Terman
Office of the Provost
Stanford University
Stanford, California
Dear Fred:
I have no personal knowledge of computers nor does anyone in our organization have any appreciable knowledge.
Sorry we can't help you out in this regard.
Sincerely yours,
(Signed, 'Bill')
William R. Hewlett
WRH/ma