What format is the EX1? Elements does not support mxf, but it does mp4. How was the footage transfered to the drive.
Best is not to work with external drives but with a internal one.
First, using under $100 consumer level software to try and edit video from a Pro http://pro.sony.com/bbsc/ssr/product-PMWEX1R/?XID=O:BPSEG_sony%20ex1:Google_PVPA_MOD_XDCAM EX1R_p_ad3 camera may not work
Second, some information to answer Ann's question
Read Bill Hunt on a file type as WRAPPER http://forums.adobe.com/thread/440037
What is a CODEC... a Primer http://forums.adobe.com/thread/546811
What CODEC is INSIDE that file? http://forums.adobe.com/thread/440037
Report back with the codec details of your file, use the programs below... a screen shot works well to SHOW people what you are doing
The Sony EX1 is a $6000 professional style camcorder. It would probably best to edit its video with professional style software, like Premiere Pro, rather than $75 consumer software.
You camcorder also shoots in XDCAM, a format that Premiere Elements does not support.
I cannot test E7 but E11 does import mp4 from an excam camera.