Need Data off Hard Drive Connected by USB

Hi. I have a hard drive from a Toshiba laptop that is toast. I connected it to my desktop running Windows 7 via a USB adapter. I right-clicked on Computer, selected Manage which took me to Computer Management and selected Disk Management. The hard drive shows up as Disk 3, Basic,, 149.05 GB, online. The 3 partitions are: 1. 200 MB Healthy (EFI System Partition) 2. 148.73 GB Healthy (Primary Partition); and 3. 128 MB Unallocated. This drive will not let me give it a drive letter and it does not show up on Computer. PLEASE help. I need this data. Many thanks.

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Ultimate, Service Pack 1, 64 bit
Processor: Intel(R) Core(TM) i7-2600K CPU @ 3.40GHz, Intel64 Family 6 Model 42 Stepping 7
Processor Count: 8
RAM: 8096 Mb
Graphics Card: Intel(R) HD Graphics 3000, -1988 Mb
Hard Drives: C: Total - 85854 MB, Free - 3116 MB; F: Total - 953765 MB, Free - 551554 MB; L: Total - 953866 MB, Free - 302450 MB;
Motherboard: ASUSTeK Computer INC., P8Z68-V PRO GEN3
Antivirus: avast! Antivirus, Updated and Enabled