Hard Drive keeps cutting out

Hello everyone!
Hard Drive troubles. My internal Seagate barracuda 250GB (which is my only drive and it has win 7 64bit on it), is acting very strangely.
So yesterday it was working fine like normal, but then I sold my graphics card, so I had to take it out of my computer. I took it out successfully, and then used the onboard graphics instead. I booted up windows like normal, but then when I got into windows, about 10 seconds later, the hard drive starts beeping repeatedly, shutting off and back on very quickly and randomly about 20 times in total. Of course windows crashed and I had to switch the power off (no BSOD though). I thought it was a loose sata power cable, but I replaced it and same happens  
The strange thing is, it never happens when booting windows, but always about 10 seconds after entering windows.
And the even stranger thing is that it doesn't happen in safe mode. I can work in safe mode for hours and nothing happens to the hard drive. And it was fine before I took my graphics card out.
So, anyone have any ideas?
Thanks