How to change minecraft build?

[fulaapan]

I need help chaning the minecraft build from 1.6.4 to 1.5.1 when playing tekkit .

[TonyVS]

you can't though the launcher you have to build it manually. and switch to http://www.minecraftforum.net/topic/939149-launcher-magic-launcher-125-mods-options-profiles-news/ with that launcher you can pick what ever version of forge/minecraft you want (will take some research on your part though)

[efflandt]

You can select a different (older) Tekkit version manually from the little gear under Tekkit in the launcher. But I don't think you can easily change which MC version you use for a newer Tekkit since an older MC may not have blocks that a newer Tekkit version assumes MC has natively. So easiest would be to go back to a Tekkit version that used MC 1.5.1 (not sure which Tekkit version that is, but something before Tekkit 1.1.10 which uses MC 1.5.2).