-My hard drive doesn´t work (not detected in the BIOS menu) if i boot my system with my graphics card connected,
everything´s fine if i´m using the integrated graphics card on my motherboard. My last PSU broke (an anlix atx 450w), so i got a new one (xtech 600w) and now this happens
-Intel Core i3 2100 (3.1 GHz)
-4Gb of RAM memory DDR3
-Running windows 7 Professional, 32 bits
-Zogis Nvidia GTX Geforce 550 ti 2Gb
-Seagate Barracuda 500Gb
Are you sure that is the problem?
Reset the bios, disable integrated graphics and try again.
In you have another boot drive(that has an OS on the drive) and it is working with the graphics card use it to boot into the faulty drive and use a software like partitionguru or diskeeper to repair the drive.