there is no reason to go with a 32 bit os anymore... (since pretty much everything has 4+ gigs of ram)
always get the 64 bit os...
And as for that package, you HAVE to get 64 bit OS otherwise it won't recognize 4+ gigs of the memory.
win7 oem ($100)http://www.newegg.com/Product/Product.aspx?Item=N82E16832116986
If you want it to be cheaper, $88 at ncixhttp://www.ncix.us/products/?sku=45271&promoid=1285