I am running SW 2006 Office Professional and COSMOS Advanced Professional SP4.1 and SP4.0 on a Dell 690 dual 3.7Ghz CPU's w/ 4Mb RAM and a NVidia 4500 (512Mb), I desing large assemblyes doing Top-Down 100% parametric models (entire model is over 400Mb of files and top assembly is larger that...
For selection of cooling towers (to select which tower from a particular manufacturer will give the capacity required for an specific application) you can use a selection program from the manufacturer, or just select the tower using their techincal brochure and the tables you will found there...