Starting in April, 2006, Indiana will join 47 other states in observing
DST. Of course SOME Indiana counties won't change their clocks until
October. (More on that later...) In August, 2005, Congress passed
an energy bill that included
extending Daylight Saving Time by about a month. Beginning in 2007, DST
will start the second Sunday of March and end on the first Sunday of
November. Those Indiana counties that are moving to Central Time
(CST), will automatically become Central Daylight Time (CDT) during
the Summer. Then in October 2006, they move the clocks BACK to
CST, at which time (pun intended?) Indiana will now be in sync with
the rest of the USA (that observes DST)
Here is the most recent map of the New Indiana Time Zones:

Map Source: http://www.indianachamber.com/pdf/CentralvEasternUpdateJan2006MAP.pdf
How to Modify your Microsoft Windows Time Zone information:
Microsoft has included a file
in all copies of the Windows CD-ROMs that came with your
computer. It is called TZEDIT.EXE, and is found in the "Resource
Kit" area. The simplest way to find
it is to do a "find" on your
CD for "TZEDIT.EXE". Click on it and the program opens and you
are presented with a list of choices. Select your current time
zone and change the dates as appropriate. Indiana users may want
to create a new "Indiana" selection or modify the one they are in,
remembering to change it again in April, 2007.
For further information, see the Microsoft Bulletin 886775 (This bulletin applies to Uruguay time zones, but the information is the same). http://support.microsoft.com/default.aspx?scid=kb;en-us;886775