STIHL :
I have a 1TB HDD and want to upgrade to an SSD to move windows and maybe other programs onto it. Would a 120GB SSD be enough for windows and can i just move windows onto the SSD?
1. You can't move "just windows" onto that.
That would require a clean install.
2. 120GB is on the wrong side of the price vs size curve. At todays prices, you want at least a 250GB SSD.
3. How much total used space is on your current HDD?