PCI E card into a PCI slot?

[#1]

Good evening colleagues
Is it possible to fit a PCI Express card into a PCI slot and what (if any) are the implications?
I want to fit one of these new eSATA cards onto my ASUS A7N8X MB but they only seem to be in PCI E format.
Many thanks TIA

[#2]

In a word no - the interface is completely different.

[#3]

Unless you specialize in large serial I/O no drive will achieve 80MB/s.
If you want good performance on real data 7400rpm drives are useless.
Why not try a 15K SCSI drive (if your pockets are deep enough)?