1. shrink your OS partition to a bit less than 120GB (in decimal)
2. Image the partition - if you have the 100GB active partition, you have to image that too
3. Install the SSD (or connect it via USB for a laptop)
4. Align and format the SSD with diskpart, see here:
http://www.sevenforums.com/tutorials/113967-ssd-alignment.html?ltr=S
If you have the 100MB active partition, that goes for that. Then you have to shrink it to 100MB and create a partition in the freespace for the OS.
5. Move the images to the SSD.
6. Make the active boot partition on the HDD inactive
7. Change your BIOS to boot from the SSD
8. Reboot
9. Hopefully I did not forget anything - LOL
For the disk operations you best use the bootable CD of this program:
BEST FREE Partition Manager Software for Windows supports all 32-bit & 64 bit Windows No-server OS.
Now if you want to make your life easy, spend $19.95 for this program:
Paragon Migrate OS to SSD - Overview It does everything for you and you are done in 20 minutes. It is very easy to use - I tested it, worked perfectly.