Eastern Front needs that your pc has some software in order to run. Let's call them basic software.
a) Original Company of Heroes 2.601
b) .NET Framework 2.0/3.0/3.5
The problem you have is related to "a)", CoH is not 2.601, you'll have to download the patches, in the main menu shows your current version.
Then download them from
here, the official site. Of course there are mirrors of direct download that you'll find if you look around
.
Besides the patches are separated in columns by product, you can use the patches from the newer versions on the "old games"... the patch is progressive, if you have vCoH 1.7 and 1.8 is from OF, nevertheless, you shall install it because the patch works on all the products, same with vCoH or OF with ToV, until you reach 2.601 update.
Once you got CoH up to 2.601, you'll be able to play EF. Of course if you have an ilegal version won't be so easy, you'll need an extra step. Eastern Front Team don't support piracy, so I can show you the path, but you'll the one who walks there(but i don't gonna show you the end of the road of course
).
So, your copy of CoH is a pirate one?
Remember to patch EF before playing, there're some nasty bugs already fixed from the v1.20.