PostGIS 1.3,1.4,1.5 can coexist in the same PostgreSQL server, but must be installed in separate databases.  This makes it a little easier to cross test different versions.  However -- all versions will share the same proj and geos dlls so you
may want to back these up libproj.dll, geos*.dll, shp2pgsql, pgsql2shp in the bin folder of your PostgreSQL install before continuing. 

--Creating a template postgis database or new postgis database  --
1) Copy the contents of this folder into C:\Program Files\PostgreSQL\8.3 or where you have installed (
(if you already have proj, geos, you can get away with just copying the lib\postgis-1.4.dll (and share\contrib\postgis-1.4) files if you want
2) Edit the makepostgis.bat and run it.
3) Now you can connect via pgAdmin III and create a new postgis 1.4 database and set template to template_postgis14



--NOTE FOR UPGRADERS --
PostGIS 1.5, 1.4,1.3  can coexist on the same PostgreSQL install but must reside in different databases, but if you wish to maintain more than one
, make sure to copy the .sql scripts into separate folders so as to not get confused

The only caveat is that there can only be one proj and one geos install, so when you copy the above, you 
will automatically upgrade your proj to 4.6.1 and your GEOS to 3.2SVN (3.2SVN has some fixes for Union topological rounding issues but is still in beta)

If you are upgrading from 1.2 thru 1.4, there are two approaches you can use.  
-- For older versions - you can only use approach 2

Approach 1:
1) Run the appropriate upgrade script located in the share\contrib\postgis-1.4 folder
(For example if you are upgrading from 1.3 to 1.4 run postgis_upgrade_13_to_14.sql
and if you are upgrading from an earlier version of postgis-14 run postgis_upgrade_14_minor.sql

Approach 2: Should work for any version even 1.1
1) Backup your existing database with PgAmin III or pg_dump (make sure not to choose drop objects before restore)
2) Create a new postgis database using the makepostgis.bat (or from template_postgis14 you have created)
3) Restore your backup into this new postgis db (again you can use PgAdmin III for this)
