Further research has taught me that the four very different font
behaviours I have been experiencing in Windows XP and Office 2000
are a problem common to this environment.

http://acharya.iitm.ac.in/multi_sys/unicode/mono4.html
(see examples at the bottom of webpage)

Apparently there are two different Uniscribe versions installed on
my computer and they may not be equally accessible to all
applications. So Office 2000 applications do not properly support
the Unicode Tamil font at this time on my computer.

I have been directed to websites which demonstrate how to find,
identify, update and relocate Uniscribe (USP10.dll) files for those
having difficulty with improperly supported fonts.

In the meantime the recent USP10.dll version that is running in
Windows XP supports Unicode fonts in Wordpad. There I can finally
see the intended font behaviour for Tamil (Latha font)with character
conjuncts (syllables and final consonants).

Unfortunately I was not able to see this proper display of Tamil
font earlier. I was however always using the keyboard and font
recommended on this site.

As far as input is concerned I understand that Tamil speakers are
popularly using transcription or code conversion (input in legacy
fonts and converson to Unicode afterward)as seen at Jaffna
Library.

http://www.jaffnalibrary.com/tools/Unicode.htm

Suzanne McCarthy