Were you using firewall software on your computer? If not then maybe you were letting in a bunch of traffic that the router's internal firewall has now put a stop to. Can't think of another reason why a router would speed things up really.
Can you give us a make/model for the PC in question? Some use different keys to access the BIOS. Such as the DEL key or F12 in some cases. In addition, when the PC boots, is there a boot page which would indicate what type of BIOS you have?