Stop converting complex sources
News recipe processing
is intensive
Buy more RAM or
Switch to a lighter-weight Linux (just reduces the base use, leaving more of what you have for the user aps)
Seriously,
My mid range W7hp Laptop came with 3G RAM, My W7pro had 8G.
I have 2G in my 32bit XP system
Calibre is not some light-weight text editor. It is also made from common building blocks, that are not optimized for a single OS . Calibre is made to run on 3 OS