what external memory would you suggest to use in order to execute all your programme and to store files?
Any suggestion is welcome. thanks.
What do you mean by external memory? If you need more memory then you should think about increasing the actual RAM in your computer. If you are talking about the speedboost whatever thing that Windows vista/7 does then any SD card works and you can keep files on it. But I've never tried it because access to these ports is several orders of magnitude slower then actual RAM.
We need more details.