It's possible to run Linux on just about anything from a 386 on up. What kind of CPU/RAM/HDD does it have?
If it's an older laptop (486 or early Pentium), there are a number of good minimal Linux distros you could try, such as Vector Linux
. If it's a Pentium/AMD 200Mhz or greater with a fair amount of RAM (32+), you could put just about any distro on it. It kind of depends what you want to use it for.