windows XP has a backup copy of cookie in a file called Index.dat
it contains a list of the cookies ... after you delete them and restart the Index.dat file puts the cookies back.
my suggestion to you is
1. download install FireFox (http://www.mozilla.org/products/firefox/
2. Turn off cookies completely on FireFox
Tools > Options > Cookies > Uncheck "allow sites to check cookies
3. Restrict your pr0n surfing to firefox only
4. Tools > Options > Clear All (after surfing for history and cache)
you might even not keep a Firefox Icon on the desktop ... she might not even notice you have another browser on there. If she does, just say you heard "it was more secure"