Windows 7 - Please Help! Lost data after re-install

Hi. I have two Seagate 3tb XT internal drives and a Hitachi drive used as my boot drive. The two xt drives were partitioned due to the 2.1tb limit using Seagate drive wizard and have been working fine. I decided to clean up my PC and re-install Windows 7. I re-installed to the Hitachi drive which went fine but now both xt drives are only showing the larger partitions and the smaller partitions are showing as unallocated in drive wizard and disc management. I cannot add a drive letter or revive the partitions without losing the data as the only options available are to format or wipe the partitions. Am i missing something obvious here? I can't see how both drives could have become damaged in the space of an hour and i definitely did not format or change anything except to the Hitachi drive. I'm not really familiar with partitioning drives but i really can't see what i'm doing wrong, i just expected to see all four drive letters as they were before the re-install.

Would really appreciate some help with this as its an awful lot of data i've lost. Thanks in advance

It is always prudent to disconnect all unneeded drives during an installation. But what you are seeing is a bit odd indeed.

I would try to pull off my data from the 2 dead partitions either by using a live Linux CD or with Recuve Download Recuva 1.42.544 - FileHippo.com

Try to recover partitions with any of these.

Paragon Rescue Kit 11 free edition.

Rescue Kit Free Edition | PARAGON Software Group - free partition software, hard disk partitioning

MiniTools Partition Wizard Free Download Magic Partition Manager Software - Partition Wizard Online and

EaseUS Partition Recovery Free Partition Recovery Software - Recover Deleted FAT/NTFS/Ext2/Ext3 Partition.

If you want to try the Live Linux way as suggested by whs above, have a look at my thread Lucid Puppy way to recover files from a non-bootable computer

If none of the above work, I helped someone a couple weeks ago with a similar problem. He was able to recover his data using Free Format Recovery Software | Recover files after format free | iCare Format Recovery Free