Well UltimaX I couldn't recall such system file which concerned with minimizing windows is edited by Bricopacks 
Bricopack is just a shell & graphic modifying pack but it does not do any performance modification 
As Asher had previously mentioned, using too much skinning software might be the cause of your problem
Sometimes not just one several of those software can cause such problems if those were not designed to be supportive to another
UltimaX, it made me wonder to ask that are you using Bricopack with a Vista Transformation pack ?