Try changing the contrast and brightness on your monitor. I had the same
problem. Also see "Excel 2007 Gridlines Disappeared" question and response by
Justin W. Hamburg who says this seems to be a new problem with Office 2007
perhaps because they use lighter colors.

"Melissa W" wrote:

Thanks! That helps alot.
That changes the gridlines for a particular worksheet. I guess that you
can't set it up to have darker lines be a default setting?

"Teethless mama" wrote:

Click on Office Button on the far left corner Excel Options Advanced
Scroll half way down you will see Gridline color and change any color you like

"Melissa W" wrote:

I just installed Excel 2007. The gridlines appear very light blue and are
hard to see. Is there any way to make the gridlines appear darker?