hex editing and unpacking dlls

Hi, i downloaded PEiD program to check if its packed or not, it says packed so i downloaded PE Explorer i opened the file and it unpacked the dll and i saved CA-EU Hakk.dll to dekstop,i edit it with HxD i put MPGH.NET instead of the other advertisment, i save file, but when i injekt it with PerX it says warning: ca-eu hakk.dll is not a valid windows image or something like that... and also i noticed two new files in desktop, "CA-EU Hakk.dll.bak" and "CA-EU Hakk.dll.(1).bak"
how can i resolve the problem?

u cant change the amounts of letters or it would give an error
so if the site is called 1234567.com change it to like example xxxxxx*****m and u'll be fine