So a year or two BACK I put a 70 GB hard drive in my computer in addition to my 500 GB drive. My buddy and I installed Linux on it for fun and I can't remember what we did but since then when I booted the computer a menu would appear and I had to choose which one to boot from. I just repartitioned the 70 gig drive with Linux on it and formatted it. Changed the boot order in startup to my 500 gig drive with windows 7 on it. The 70 gig also has windows 7 on it now but when I START my computer it tries to open the menu but just sits at a black screen with a white underscore blinking at the top. I am at a total loss and anything would be a big help.Another method for dual booting is to have each drive independent of each other....
In this method the 2 OS's never see each other and it MAY help diagnose if it is indeed the 70G HDD as the culprit.

Remove the existing Win7 install on the 70G via the other Win7 install.
When that is finished power down.
Hook up only the 70G  and re-do the install of Win 7 to it...Boot it up and install all neccessary system drivers from the MBoard driver CD.

Re-connect the 500g on the SATA 0 connecter with the 70G on SATA 1... (Note: on some boards it may be Sata 1 and 2 respectively )
Now when you boot load setup/BIOS...both drives should be listed...select which one you want to use for this session ...move it to the top of the boot order and press F10 to "save changes and exit"...

If the 70G HDD still boots SLOWLY in this isolated setup then it is the HDD that has issues.
Hope this helps.