Go on this website http://www.emachines.com/support/product_support.HTML enter your PC name and so on and you will get all drivers which you might need.
Downloading ntoskrnl.exe off of the internet is a very bad idea; it is probably the singularly most important file in Windows XP, and it could easily be tampered with to put a rootkit on your...
If you have the XP install disk available, drop it in the CD drive and reboot the computer. Before you do, make sure you copy anything you want to save to a floppy disk, a CD or a secondary drive...