The cursor in Vista is really hard to see. It's a single pixel wide, even if you have really good vision, it can be hard to see the cursor since it is so thin and easy to miss. The easiest way to make the cursor easier to see in Vista is to increase the thickness.

To do this go to the Control Panel and select Ease of Access, then Optimize visual display. Scroll down to the section called Make things on the screen easier to see. In this section is an entry called Set the thickness of the blinking cursor. You can increase the thickness here, and they show a sample so you can see what effect this will have.

Once you have the thickness set to your liking, click Save and your cursor size will be increased.