system restore question

Hi;

Before installing a driver, I created a SystemRestore and named it "BeforeInstall" that if this driver worked weird, return the system to before installation. After installing I created another SystemRestor and named it "AfterInstall". Then I back to the system restore list and both of them were there. But now when I tried to back to "BeforeInstall", it does not exist and has been erased. why? 

What was wrong?

What I should do to create a few SystemRestor?

Gratefully

martinmiciciday