You're not the first person to ask for this sort of question, and be told that reports of "All Software" for "All Computers" are usually not a good idea.
See http://www.myitforum.com/forums/m_207727/tm.htm or http://smsug.ca/blogs/garth_jones/archive/2007/05/31/417.aspx for an explanation why.
Basically each PC can have around 200 to 300 items in "Add/Remove Programs", even if you limit it to "Installed Software" it can still be hundreds per PC. Multiply that by the number of PCs, and you start to quickly get into reports that have millions of rows.
My advice is to tackle your problem from a different angle. For example, start with the Software 1A or Software 6A reports in the Asset Management category. These will give you totals for certain applications in certain collections. You can then start drilling down into the application you think are relevant for your exercise and see the list of installed PCs. You'll see a lot of applications you will probably decide to ignore.
You could create collections with the PCs you need (San F, LA, San D etc.) based on whatever criteria you thing is most appropriate (PC Name, OU name etc.).
Regards,
Tom Watson,
E-Mail: Tom_
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Blog: http://myitforum.com/cs2/blogs/tom_watson