BuildOS trouble VISTA

[DJx79x]

i keep having trouble with buildOS. i have vista and every time i created a rom it would either add too much and get an error or when i finally was able to flash the rom i would always get an RUU error is it because of vista and if it is can it be fixed i turned off the usb connection through mobile device center i even did the modacco steps for flashing with vista and those worked the first time i flashed my phone to wm6 also is there a way to see how much space you have left before you start building the rom