There are three variables that play into your computer's ability to record a lot of tracks at once. The first is the processor, the second is the memory, and the third is how fast your computer writes to your hard drive.
Without the specs on your laptop I have no way of knowing which of the three it might be. I do know that processors on laptops are almost impossible to upgrade, and the memory isn't a picnic either. Any "external" hard drive you get is going to write 100 times slower than the internal one already installed. So that leaves you two options. Either spend the money on upgrading the laptop, which might not even be possible, or get a new one.
Or... just record less tracks at once. Also, make sure you're not running any real-time effects while you're recording, that'll MAJORLY slow your computer down.
You could always try defragging your hard drive, but I doubt that'll improve the performance of the computer noticably.