windows server 2008 - Installing a (sort-of) weakly-named .dll to the GAC -

i need migrate programs 1 server another. in process, found missing .dll - tracked down on original server. both on file system (in seems storage directory, not linked anything) , gac. took .dll storage directory on new server, , tried install using gacutil - failed message:

failure adding assembly cache: attempt install assembly without strong name

this seems strange me has been installed on previous server (the version #s of 2 .dlls same). however, not have source code .dll, possible version in gac re-compiled named, , version in "storage" not updated.

one possible work-around install .dll manually. in c:\windows\microsoft .net\assembly\ lives .net 4.0 separated gac directory structure, create gac_msil\[.dllname]\v###__[publickey]\ folder, using same public key gac implementation on old server, , put .dll file in there. however, .dll not compiled .net 4.0 (or .net 3.5, don't think) - work? or changes have make work?

i don't know how manually install "old" gac, 1 windows explorer gui, directory structure not exposed me. answer (https://stackoverflow.com/a/382318/1675729) seems indicate there underlying structure attempt similar method of manual installation - if work, can give me more information how access structure?

of course, if there way install weakly-named .dll gac, ideal. .dll not going cause .dll-hell problems, has specific purpose (and name), , used 1 program. don't know how this, however, , since seems opposed purpose of gac, i'm not surprised there's lack of information it.

i'm open , suggestions, , happily provide more information can - i'm unsure of what's important note here.

thanks much!