If your laptop is old enough to have an IDE hard drive, it could be rather expensive to get a new one.
But if it is IDE and also has a battery with less than half of its capacity left, you might want to try one of the new SSDs. Some of them are now cheaper than a laptop IDE hard drive and can make a laptop with a failing battery still usable since you can turn them on and accomplish your task and shut them down in less time than it takes the HDD version to boot thus using a lot less power from an old battery.
There are few things more frustrating than watching a laptop s l o w l y booting windows and then s l o w l y shutting down when you know the battery is probably going to quit while it has the hard drive writing.
An SSD and an install of lxde could make a lot of these old laptops usable again at a time when you can not justify spending much money on them.
And what is more, they are likely to run twice as fast as they did when new.
Another thing you might want to consider is that some of the video cards on older machines do not have drivers that can output to the aspect ratio of the new wide 22" monitors.
Some of them will output the right aspect ratio at the native resolution of the monitor but will not work if you try to set it at a lower resolution so that old eyes can read it.
Many people don't mind having circles show as ovals so they get along just using a 3 to 4 apect ration which the card and the monitor will do.
I can not imagine an artist putting up with that though.
So you might want to look and what resolution your old computer can do before buying a 22" monitor.
My 22" monitor has a native resolution of 1680 x 1050.
I have to run it at 1440 x 900 in order for me to see it where it is sitting across the room.
This works in linux but the drivers for that chip set for windows will not allow anything but 1680 x 1050.
This makes that Lenovo machine which dual boots with XP very annoying when booted in windows.