NANAOMAN, i dont know if this helps but you can get wireless pc to tv converters like this one on ebay
http://cgi.ebay.co.uk/ws/eBayISAPI.d...154154411&rd=1
i presume you can get the sam kinda thing for a vga, if not a converter would bbe needed like im planning to get so i can avoid my pc alltogethher, bbut there not cheap
those mirrors are called cold mirrors, i think, its what people use then they make the compleat diy projector, ie with out the ohp, although i cant vouch for how well they work
p.s my ohp cam wahay