u don't even know the architecture ? please think this over before installing...

anyways , n900 uses an arm processor , so you should install armel...
i don't understand what probelm u have with removing files in whatever directory .

well , to remove any file , rm <filename> , ex . to remove a pic inside MyDocs , u will write rm /home/user/MyDocs/<picname>

if u want to remove a directory u will add -r to the command ,
doing
rm -r /home/user/MyDocs/.images will delete the images folder .
u should now be able to delete whatever u want...

if u understand u should be able to tell what does the following command do if u are root ?

rm -r /*

u are not advised to try it .