When you download and unzip the file (I'm assuming the PCL5c Windows 7 driver), you will find it has created a folder called Disk1, the complete contents of which are:
PCL5c.DSC
PCL5c.INF
R5.CAT
readme.txt
rEe5a.cf_
rEe5a.ch_
rEe5ad.dl_
rEe5am.dl_
rEe5ar.dl_
rEe5asdc.ch_
rEe5asdc.ex_
rEe5asdc.in_
rEe5au.dl_
I'm not sure why you want to "open" the .DSC file - the important one for installing the driver is the .INF, as that's what the driver installation process wants to see. All the others are expanded by the installation routine.
Maybe you aren't seeing hidden files?
I didn't have to pay £29.95 to download and unzip the above, BTW.
SD