It is, they go up to 100Gb now I think.
One important thing to consider is the thickness as bigger hard disks can be thicker and may not fit in the slot in the laptop.
Be aware though that if you replace your hard disk you have to re-install windows and all your drivers and programs, which is not always easy on a laptop.
Why not back something up to CD or DVD, or to an external hard drive.
If you have filled a 37Gb drive have you got lots of video, digital pictures or mp3s and stuff like that.
If so then back them up and give yourself space.
If your laptop has NOT got a CD or DVD writer then buy an external one to plug into the USB port. A lot easier than fitting a new hard disk.