Well, I thought SetCurrentDirectory didn't work like that, but if it does then there is no reason why that implementation couldn't be used. GetCurrentDrive ought to verify that second character is indeed ':' (preparing for UNC names) but that should work, too. Using wide character versions would be preferred, though.
Ok, I've had time to check this on win98 and SetCurrentDirectory doesn't work like this. This is doable as its done in wcmd: G:\wine\programs\wcmd>c: C:>cd windows C:\windows>g: G:\wine\programs\wcmd>c: C:\windows>
nog.