DES Encryption: libdes vs SSLeay (OpenSSL)

I'm trying to get SSLeay to produce the same results as libdes. I have
a copy of the des.exe program that uses libdes v4.01. I also have
SSLeay 0.8.1, both written by Eric Young.

I am unable to produce identical encryted files using libdes and
ssleay. The commands I am trying are:

des.exe -E -k 12345678 input.txt output.enc

ssleay enc -des -e -k 12345678 -in input.txt -out output.enc -iv
0000000000000000

Does anyone know why this might be? Surely if the Initialisation
Vector is set to 0 in SSLeay, it should give the same results as the
older libdes library?

Thanks,
Campbell