This comes up fairly often.
But the fact is that there's just no way to turn PowerPoint into graphics that will import into Premiere Elements in any readable quality. To get readable text, you really need to create the text in Premiere Elements.
On the other hand, someone at Premiere Elements support site http://Muvipix.com found this solution that may help.
IIRC, the latest version of PowerPoint can Export as TIF, which will Import fine. The version will matter.