Normally desktops can be left on indefinitely. I can't say about this particular labtop. One thing you should do if you have not already is make backup copies of all files you do not want to lose. This can be done on CD-Rs or floppy discs.

One drawback to keeping the computer on all the time is that eventually, as the memory begins to fill, the operation becomes slower. While this is not as bad with Windows XP as other operating systems it is still something to consider.   If there is a weakness in the hard drive it might last longer if the computer is left running than if it is turned off and on.