To use the play.bat and stopplay.bat, you must have an environment variable called UserName set to your logon name.

Creating the environment variable.
1.  Right click on the My Computer icon on the desktop and choose Properties.  If you don't have a My Computer icon, click Start - Settings - Control Panel.  From the control panel choose System.
2.  Click on the Advanced tab.
3.  Click on the Environment Variables button.
4.  You should have a window open now with a listing of User Variables for you and one for System Variables.  If you don't have Administrator priviledges you can only edit your User Variables.  And that's what we are going to do.
5.  Click on the New Button in the User Variable box.
6.  Enter UserName for the Variable Name.
7.  Enter your log in name for the Variable Value.
8.  Click OK.  You should now see the new User Variable.

To make it easier to run, create a shortcut on you desktop.  
1.  Right click on the screen.
2.  Choose New/Shortcut.
3.  The Create Shortcut Wizard should open.  On the first screen type cmd.exe.  Click Next.  On the second screen enter the name you want displayed under the shortcut.
4.  Right click on the shortcut you just made and choose Properties.
5.  The Target line should read %windir$\system32\cmd.exe.  Leave it like that.
6.  The Start In line should be changed to be your My Documents folder.  Enter C:\Documents and Settings\<username>\My Documents.  Naturally you want your username instead of <username>.

Now before you're ready to use this program, you need to put it into your My Documents folder.  It also needs to be edited.  Open is with Notepad then look for the line that starts rem IMPORTANT!.  You need to edit this line so it starts the proper game for you.  The easiest way is to right click the icon you use to start the game and copy the Target line, then paste it over my start up line ("C:\Program Files\EA GAMES\The Sims 2 Mansion and Garden Stuff\TSBin\Sims2EP9.exe" -w -r1280x1024) in the file.  

If you don't want to change the modularstairs script delete these four lines:
rename "C:\Program Files\EA GAMES\The Sims 2\TSData\Res\Catalog\Scripts\modularstairs.txt" "modularstairs.txt.original"
rename "C:\Program Files\EA GAMES\The Sims 2\TSData\Res\Catalog\Scripts\modularstairs.txt.%1" "modularstairs.txt"
rename "C:\Program Files\EA GAMES\The Sims 2\TSData\Res\Catalog\Scripts\modularstairs.txt" "modularstairs.txt.%1"
rename "C:\Program Files\EA GAMES\The Sims 2\TSData\Res\Catalog\Scripts\modularstairs.txt.original" "modularstairs.txt"

If you want to tailor the other scripts, just copy the lines for the modularstairs and replace the filename.


One last step...
For each of your themes, that you'll be using, you need to come up with a one word extension.  This extension needs to be added to the appropriate The Sims 2 folder and the scripts you'll be using with that theme.  For example, The Sims 2.medieval and modularstairs.txt.medieval.  These theme specific folders and scripts must be set up by you prior to running my batch programs.

Now you are ready to go.

Double click on the cmd shortcut.
In the DOS window that opens you should see the prompt pointing towards your My Documents folder.

Enter "play <theme>"  The files will be renamed so you can use your themed set and the game starts up.  You must leave the DOS window open while playing your game.

Play your themed game.

After you quit your game, the files will be renamed back the way they started.


