How Do I Prevent Photos In A Cell From Disappearing?

I have created a spreadsheet of book I am wanting to purchase and I am
putting photos I get off the web of the books into the spreadsheet. Before
I put them into the cell I convert them to a .jpg file using Irfanview.

When I get done inserting the photo I right click on the photo in the cell
and go to "Size and Properties" and go to the "Properties" tab and select the
"Move and size with cell" option and make sure the "Locked" box is also
checked. I then close out the dialogue box.

I save the Excel file (I have Excel 2007 and have saved it as a .xls and
..xlsx file) and close it out. When I save the file I get a "Compatibility
Checker" dialogue box that tells me that "some cells or styles in this
workbook contain formatting that is not supported by the selected file
format. These formats will be converted to the close format available.".
I've closed out this box and let the file be saved.

Within a short when I open the Excel file in either extension (.xls or
..xlsx) the photos disappear.

How do I correct this problem?