Don't STP off!!! The reason that your P.C's are taking there time in downloading their policies is because of STP, but you must tell STP that those P.C ports (Access Ports) are indeed access ports, you need to turn on "portfast" (Cisco) "Edge Port" (HP/Netgear)
The arp look like rouges, remember that arps are requests from devices but they can also come from devices annoucing themselves into the network, saying "hello, I am a router. Hello I am a router" gratuitous arps!!!
WS is the only way to track down the arps, but arps are a part and parcel of a network, if you want to reduce them in a network or reduce the scope of their broadcast domain then use vlans
Hope this helps