belkin and netgear routers

i,ve got 2 pcs, 1 upstairs and the other downstairs directly under each other. both are internet sharing using ethernet cards. my problem is, i pay for 5mbps broadband, which is what i get when connected but when connected through any router my pc is dropping down to 1mbps even when the other pc is unplugged. take out the router and my speed goes back to normalay advice