|Please list your complete system specs & include the make/model of your external HDD. As stated above, it may simply be a motherboard driver issue.|
"may i no the resion and my smps is of 850watss 2.5 TB harddisk"
The fact that you called your power supply an "smps" tells me you're probably from India. And just because it's 850W doesn't mean it's any good. In the US, a decent quality 850W PSU that's 80 plus certified, has active PFC & a single +12v rail generally sells for at least $100, that's approx 6150 Rupees. Is that about what you paid? A cheap low end "smps" can cause all sorts of problems.
message edited by riider