slow PC have so many reasons, it could be that you have so many programms that runs when windows starts, your hard drive is full, your memory is not big enough for the programs that you are running. etc, for me its is a waste of time tracing all this factors. what i would normaly do or advice to someone is to reformat the hard drive and install a fresh copy of windows. most often i find this very effective. because i erases all temporary files that are hard to find, unwanted programs and eventually stuborn virus.
you might also like to spend a bit of a cash put atleast 1gb of memory in your system, operating system like vista uses a lot of resourses at thats vista alone, it does not include the programs you want to install and run. they come cheap now a days (try ebay).
now your outlook express need to be reinstall so it can work properly again.
about the extra language go to microsoft website and look for the language pack that you want and download it.
so to summarise:
• re-format your hard drive install new OS (pref XP PRO).
• Uprage memory 1gb atleast or bigger.
• downlaod language pack from microsoft website.