Most laptop battery specs are based on real life crunch tested using benchmarks to back up the claims. Most fall in the 2-3 hour mark for normal home boxes. You will find some that may exceed, but they are likely stuffing more battery into the box.

The price range of solutions in $1000-$1500 will net you your best bang for the buck in solutions with all the features spoken. New replacement models come in July and many more laptops will have wireless in them.

With Win XP you won't see much performance gain going above 512MB, diminishing returns for you $$'s spent. Most laptops go to 512MB of DDR memory, look for DDR when checking the memory.