Nokia :: N97 Application Incompatible Warning

i did a factory reset after installing the new firmware & all of a sudden the device seems to act a lot faster and better. It had issues after the update, but i formatted the whole device (first the memory card, second the mass memory, and third the c: ) and it seems to be workin a lot better. However, the inbuilt themes look dull. I went to www.mibile9.com and downloaded a couple of s60v5 themes. While installing, i get a warning, 'application is incompatible with this device. Continue anyway?' would it be safe to install these? I know they're not viruses because a friend installed them on his 5800XM with no problems. I'm wonderin if installing an 'incompatible' theme would make my N97 suck again. I've got another question. As far as i know, the 5800XM and the N97 use the same OS. The themes installed fine on my friend's XM, with no warnings (other than application is untrusted). Why am i receivin the incompatible warning on the N97 then? Laugh, and the world laughs with you. Cry, and the world laughs louder :-)