Download SolidCAM_2012_SP3_English_64bit.exe and one or more archives with language localization needed from folder ..Win64Localizations
Install SolidCAM 2012 SP3 English 64bit (run SolidCAM_2012_SP3_English_64bit.exe)
1.3. Unpack all folder from your localization archive to (by default C:Program FilesSolidCAM2012) and overwrite original ones