XP has built in Plus! theme support
If your 9x themes are in the following folder C:\Program Files\Plus!\Themes you won't even have to browse for the themes, XP will display them. To change your current theme, instead of using a seperate program, you simply need to use the "Display Properties" panel, it'll be the first tab on the panel
There is one minor problem though, your Plus! themes will change your "Luna" style theme to the older 9x style, and IMHO it doesn't look quite as good under XP, kind of blocky. You can edit the theme file to prevent this, either adding a different one of the three default "Luna" styles to each Plus! theme, or do what I do and simply change the "Luna" to what you want and use it for all the Plus! themes. Look over the following text, it's one of my Plus! theme files (FFVII), and will give you an idea if you compare it to a normal theme file what I've removed
[CLSID\{20D04FE0-3AEA-1069-A2D8-08002B30309D}\DefaultIcon
DefaultValue=%ThemeDir%Ff7\FF7-cloud.ico,
[CLSID\{208D2C60-3AEA-1069-A2D7-08002B30309D}\DefaultIcon
DefaultValue=%ThemeDir%Ff7\FF7-castle.ico,
[CLSID\{645FF040-5081-101B-9F08-00AA002F954E}\DefaultIcon
full=%ThemeDir%Ff7\FF7-cloudB.ico,
empty=%ThemeDir%Ff7\FF7-cloudA.ico,
[Control Panel\Cursors
Arrow=%ThemeDir%Ff7\FF7-arrow.cu
Help=%ThemeDir%Ff7\FF7-help.cu
AppStarting=%ThemeDir%Ff7\FF7-end.an
Wait=%ThemeDir%Ff7\FF7-Tifa.an
NWPen=%ThemeDir%Ff7\FF7-pen.cu
No=%ThemeDir%Ff7\FF7-no.cu
SizeNS=%ThemeDir%Ff7\FF7-Size NS.cu
SizeWE=%ThemeDir%Ff7\FF7-Size WE.cu
Crosshair=%ThemeDir%Ff7\FF7-cross.cu
IBeam=%ThemeDir%Ff7\FF7-beam.cu
SizeNWSE=%ThemeDir%Ff7\FF7-Size NWSE.cu
SizeNESW=%ThemeDir%Ff7\FF7-Size NESW.cu
SizeAll=%ThemeDir%Ff7\FF7-move.cu
UpArrow=%ThemeDir%Ff7\FF7-up.cu
DefaultValue
[Control Panel\Desktop
Wallpaper=%ThemeDir%Ff7\FF7-BACKGROUND.BM
Pattern=(None
TileWallpaper=
WallpaperStyle=
[AppEvents\Schemes\Apps\.Default\.Default\.Current
DefaultValue=%ThemeDir%Ff7\FF7-default sound.wa
[AppEvents\Schemes\Apps\.Default\AppGPFault\.Current
DefaultValue=%ThemeDir%Ff7\FF7-program error.WA
[AppEvents\Schemes\Apps\.Default\Maximize\.Current
DefaultValue=%ThemeDir%Ff7\FF7-restore up.WA
[AppEvents\Schemes\Apps\.Default\MenuCommand\.Current
DefaultValue=%ThemeDir%Ff7\FF7-menu command.WA
[AppEvents\Schemes\Apps\.Default\MenuPopup\.Current
DefaultValue=%ThemeDir%Ff7\FF7-menu popup.WA
[AppEvents\Schemes\Apps\.Default\Minimize\.Current
DefaultValue=%ThemeDir%Ff7\FF7-restore up.WA
[AppEvents\Schemes\Apps\.Default\Open\.Current
DefaultValue
[AppEvents\Schemes\Apps\.Default\Close\.Current
DefaultValue=%ThemeDir%Ff7\FF7-restore down.WA
[AppEvents\Schemes\Apps\.Default\RestoreDown\.Current
DefaultValue=%ThemeDir%Ff7\FF7-restore down.WA
[AppEvents\Schemes\Apps\.Default\RestoreUp\.Current
DefaultValue=%ThemeDir%Ff7\FF7-restore up.WA
[AppEvents\Schemes\Apps\.Default\RingIn\.Current
DefaultValue
[AppEvents\Schemes\Apps\.Default\Ringout\.Current
DefaultValue
[AppEvents\Schemes\Apps\.Default\SystemAsterisk\.Current
DefaultValue=%ThemeDir%Ff7\FF7-beep.wa
[AppEvents\Schemes\Apps\.Default\SystemDefault\.Current
DefaultValue=%ThemeDir%Ff7\FF7-beep.WA
[AppEvents\Schemes\Apps\.Default\SystemExclamation\.Current
DefaultValue=%ThemeDir%Ff7\FF7-fight.wa
[AppEvents\Schemes\Apps\.Default\SystemExit\.Current
DefaultValue=%ThemeDir%Ff7\FF7-exit windows.WA
[AppEvents\Schemes\Apps\.Default\SystemHand\.Current
DefaultValue=%ThemeDir%Ff7\FF7-critical stop.wa
[AppEvents\Schemes\Apps\.Default\SystemQuestion\.Current
DefaultValue=%ThemeDir%Ff7\FF7-empty recycle bin.WA
[AppEvents\Schemes\Apps\.Default\SystemStart\.Current
DefaultValue=%ThemeDir%Ff7\FF7-startup.WA
[AppEvents\Schemes\Apps\Explorer\EmptyRecycleBin\.Current
DefaultValue=%ThemeDir%Ff7\FF7-win.wa
[Metrics
IconMetrics=76 0 0 0 75 0 0 0 75 0 0 0 0 0 0 0 248 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 144 1 0 0 0 0 0 0 0 0 0 0 77 83 32 83 97 110 115 32 83 101 114 105 102 0 0 46 87 65 86 0 0 0 0 0 0 0 0 0 0 0 0
NonclientMetrics=84 1 0 0 1 0 0 0 13 0 0 0 13 0 0 0 18 0 0 0 18 0 0 0 244 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 188 2 0 0 0 0 0 0 0 0 0 0 65 114 105 97 108 0 109 101 115 92 70 105 110 97 108 32 70 97 110 116 97 115 121 32 55 32 40 104 105 103 104 32 15 0 0 0 15 0 0 0 248 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 188 2 0 0 0 0 0 0 0 0 0 0 77 83 32 83 97 110 115 32 83 101 114 105 102 0 108 32 70 97 110 116 97 115 121 32 55 32 40 104 105 103 104 32 18 0 0 0 18 0 0 0 245 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 144 1 0 0 0 0 0 0 0 0 0 0 77 83 32 83 97 110 115 32 83 101 114 105 102 0 108 32 70 97 110 116 97 115 121 32 55 32 40 104 105 103 104 32 245 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 144 1 0 0 0 0 0 0 0 0 0 0 77 83 32 83 97 110 115 32 83 101 114 105 102 0 108 32 70 97 110 116 97 115 121 32 55 32 40 104 105 103 104 32 245 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 144 1 0 0 0 0 0 0 0 0 0 0 77 83 32 83 97 110 115 32 83 101 114 105 102 0 108 32 70 97 110 116 97 115 121 32 55 32 40 104 105 103 104 3
[boot]
SCRNSAVE.EXE=%WinDir%\System32\ss3dfo.scr
[Other]
WindowsMediaPlayerSkin=TDK Digital Mixmaster.wmz
[MasterThemeSelector]
MTSM=DABJDKT
