help me reinstall OS X

my girlfriends macbook is acting very strange.
it has windows xp on it with boot camp

it has ran fine but is now acting up.
about 3 times a day OS X becomes very slow and when you try to launch a program that is not already open, it says Application Cannot be launched. this is always fixed after a VERY LONG restart

i want to try to reinstall OS X. I have an external HD that can back up all the files and docs.

When i reinstall OS X. I am going to format the OS X partition. TWO QUESTIONS:

1. How do i get rid of all the extra languages in OS X to save on space during install?

2. How do I put the files and preferences back on the MacBook after reinstallation? Is there a way to keep my safari preferences and passwords? or do i need to pretend like theyve never been saved before?

Thanks for you help
Blake

 

no luck there, nothing to repair on first try

 

i did all of the above mentioned tasks. it came up with nothing wrong and nothing to be fixed.

im still have the random errors

 

its not that the apps launch slow, its that they fail to launch. an error message comes up saying iTunes failed to launch.
It is all applications
a restart used to fix it everytime
a restart now fixes it MOST of the time

 

if i copy the home folder onto an external hard drive. and then reinstall os x. and transfer the contents of the home folder back on to the macbook will i have kept all of my preferences, passwords etc..