i have 2 ext hard drives both powered by power supplies and connected by usb. this problem has only just started happening when they or 1 is connected but not powered up i get an internet connection of 1.2MBS down but as soon as either are powered up the connection drops to 350KBS everything is fine until power is applied to hard drive(s) both drives have been scanned for virus etc, very annoying and very hard to find anything on internet that even remotely refers to it - can any one help please

Coudl have a psu problem and the drives are drawing to much power. Could also have a magnetic interference when the hd revs up. Do you have wired internet or wireless? how is your conection set up. Are the drives shared on your network? Intel DP35DPM Socket 775 Motherboard Intel Quad Core Kentsfield 2.4Ghz Q6600 CPU Ultra 4096MB PC6400 DDR2 800MHz Dual Channel 2X1024

wired internet to this computer, have made sure everything else in network is switched off & disconnected,both drives have own power supply,this is only just started happening were perfect before, doesn't matter if 1 or 2 drives are connected??????