Clone determines change drive letters

Hello
I made a clone hard drive with Acronis True Image 2010 and it worked, but I found myself with the letters changed in one unit:
the original disk was partitioned as C and D, and later became C and F.
Similarly, the two writers have changed their letters E and F to D and E.
This resulted in an update of Windows, which fortunately has agreed, because I recognized the system as the original.
The procedure was performed with the Acronis Recovery CD Menagerie.
I must point out that the clone was performed on a different disk:
was originally on a hard drive Seagate Barracuda, while the clone on a Western Digital Blak, but both the 500 GB.
Wonder if you bypassed this small incident, or if you know of a better procedure to overcome this problem.
System Data:
Professional 32-bit Windows 7
Hard Disk-500GB partitioned into C (120 GB) as a system, and D (380 GB) for data
Mainboard Asus P7P55D Evo
Intel i5-750
4 Giga Ram
I apologize for the translation is not precisely correct.
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