Premiere Elements comes with many codecs, and others are added when you install the required Quicktime... what are you trying to import that will not work?
NOTE - DO NOT DOWNLOAD CODEC PACKS !!!
On what computer system is your Premiere Elements 10 running? And what video card/graphics card does it use?
If you have Windows Media Center dvr-ms files that you want to edit in Premiere Elements 10 Windows, I believe your answer will be in converting them to regular MPEG2.mpg rather downloading and installing any codec
The other aspect of this, besides your codec consideration, is any copy protection associated with the dvr-ms.
I would suggest that you should be looking for a good conversion method for DVR-MS (no copy protection involved files) to regular MPEG2.mpg. I would think to expect any downloaded DVR-MS codec to target the playback of the file in Windows Media Center and not the recognition of it by Premiere Elements.
Please review the suggestions and determine if any work for you.