Windows XP is very slow after hibernation
How to troubleshoot hibernation and standby issues in Windows XP
basically, reduce the load before hibernating, also make sure hiberfil.sys is a contigeous file (disable hibernation, defragment the drive, re-enable hibernation).
mind you, XP hibernation at the best of times is a dodgy affair, and the more memory a system has, the worse it gets. laptop hard drives aren't exactly stellar performers, it was bad enough in the old days when laptop had maybe 256 or 512 MB RAM, now with 2 GB and more, it's often unbearably slow.