Is there an easy way to 'unpatch'?

I'm currently using the latest version of warband, when I try to install freelance 1.5 it tells me that it will "most certainly not work" unless I'm using the correct patch.  So aside from reinstalling the game, is there and easy way to get to 1.143? 

Thanks for any replies.

here you go :
http://173.192.225.169/mb_warband_setup_1143.exe

You have to install the game again... if you want to keep the current version of Warband, change the folder's name during the installation (to "Mount&Blade Warband 1.143", for example) You'll have warband installed twice, with two different versions.

If you're running 1.143 and want to play Freelancer I would recommend downloading Warband Enhanced, it's more or less the same as native though includes a load of decent gameplay modifications including a more developed version of Freelancer than this one