ummm
devil here explained it
but since it seems like ur a novice im gonna try and explain it in details
longhorn transformation pack tho it seems like a program doesnt exactly install as one
those visual stules and eye candy u see ?
are all in system files
ofcourse the windows default system files have the default look
therefore for the new look what these transformation packs do is REPLACE the UR system files with the new ones
the mac os treansformation pack does have an uninstall option in the add/remove program list
all this depends on the autho
now basically according to the updates uve installed ull have ur file versions acc. to that
for eg. files for winxp is diff , if u have sp1 u have a newer version and if u have sp2 u have a diff version
therefore the transformation pack must have a matched file version for u
what these authors do is edit the system files itself and add their BMPs and other images .. while ofcourse replacing the default ones
these new system files are then packed into that exe and submitted
for ur information SYSTEM files include
.sys
.dll
.cpl
even .exe
now like i said the transformation pack replaces these files all we need to do is replace them back with our original ones
which is on our winxp cd
here is where SFC or System File Checker comes in play
it checks the files u have with the ones on the cd
if it finds somethign different it replaces the original file from the cd on ur hdd
this i said ofcourse as a last option IF the uninstall doesnt work
in that case u need to goto start => run
and type the following
note the space between "SFC" and "/"
i apologise for the confusion i created but SFC is NOT for uninstallin programs !
nice explanation raven though i was aware of this tutorial.... 
