Replace tabs with spaces in vim

Once you've got expandtab on as per the other answers, the extremely convenient way to convert existing files according to your new settings is:

:retab

It will work on the current buffer.

IIRC, something like:

set tabstop=2 shiftwidth=2 expandtab

should do the trick. If you already have tabs, then follow it up with a nice global RE to replace them with double spaces.

If you already have tabs you want to replace,

:retab

Try

set expandtab

for soft tabs.

To fix pre-existing tabs:

:%s/\t/  /g

I used two spaces since you already set your tabstop to 2 spaces.