Can you give me the title of  a Movie which must be about 10 years old
and features  the main character(businessman or architect) MARRYING A
BEAUTIFUL UNKNOWN WOMEN WHO ULTIMATELY HAS HIM COMMiTtED TO A MENTAL
INSTITUTION by alleging that his is insane? hE ULTIMATELY KILLS HER IN
THE MENTAL INSTITUTION WHILE SHE VISITS AND HE then is released to
care for his child of the marriage.

I believe you are remembering "Dream Lover," a rather good little film
from 1994 which starred James Spader as an architect whose
manipulative wife has him sent to a mental institution where, in the
end, he kills her, knowing that he can get off on an insanity plea.

"A divorced architect (Spader) swears off women until he meets the
exquisite Madchen Amick. In no time at all they're married and having
kids. But slowly Spader begins to suspect that his wife is more than
she seems... Spader becomes extremely jealous and hits her. Her
reaction is to have him committed for wife battery. After the initial
commitment he appears before a Judge and gets another 100 days in the
mental hospital. At this point we're getting confused because the
script isn't strong enough to support all this.

To give away the ending it is revealed Amick has been plotting all
this from the beginning but Spader says there's a flaw in her plan.
And he kills her saying he can never be held responsible because he is
clinically mad."

My Google search strategy:

Google Web Search: "dream lover" "james spader"
://www.google.com/search?hl=en&q=%22dream+lover%22+%22james+spader%22

If this is not your movie, please request clarification so that I may
resume the quest.

Best regards,
pinkfreud