Windows 7 - cannot boot windows 7, boot to black screen with blinking line

I upgraded my pc with a 120gb ssd from a 500 gb HDD. I installed Windows 7 on the ssd and formatted the old drive and thus removing its windows installation, however i did not remove the 100 mb system partition (did not know how to).

When I restarted the computer it showed a black screen with a blinking line in the top left corner, at the same moment it ussualy displays the windows startup logo.

I disconnected all other drives but my ssd and reinstalled Win 7 after having formatted it. It worked fine for hours, and I was able to boot without problems. I had disconnected all drives but my ssd while installing windows 7 but when i reconnected the old drive (on which there was still the 100 mb system partition) the black screen with the blinking line was back. The ssd is in sata1 and Bios sees all drives.

it would be great to be able to resolve it without reinstalling windows a third time.

thank you very much in advance.

You will need to go into your BIOS set up and select witch hard drive to boot to.

Make sure the SSD still boots without the HD, then plug the HD in, open an elevated Command Line, use Diskpart to wipe the HD: Disk - Clean and Clean All with Diskpart Command

If you have data on the HD, you can wipe the SysReserved partition by itself using free Partition Wizard bootable CD, or after bringing partition into focus with Diskpart use Delete Partition Override

Set SSD as first to boot in BIOS setup, after DVD drive.

Thank you for your replies.

I forgot to give that info.

The ssd doesnt boot by itself either. it still produces the black screen which comes right after the motherboard logo in bootup. The bios boot is set to choose the ssd first, both with or without the HD installed. Nothing works.
I can't even get to the advanced boot option menu. f8 onlyu triggers boot device choice. choosing the ssd from here still halts the computer at a black screen.

I plugged the ssd into another pc as secondary drive. It seems fine and all files are seemingly there. It is like it can't find some bootup files or something when it is on its own.

problem has been resolved.
Though not without reformatting everything.
I formatted the ssd, installed windows 7, booted with the hdd installed that i suspect caused the trouble. I guided bios to boot from the ssd hitting f8 early

(with the last win 7 install it wanted to boot from the hdd even though bios boot priority had ssd as first, so this time i tried to use the f8 boot device choice).

Surprisingly it worked, and in windows i could follow #3 reply to clean the old hdd to get rid of the 100 mb system partition, and set up a new partition on it.

thank you for your help