How to dycrept

Hello everyone
My problem is I tried to encrypt my external hard transcend with Bitlocker and also I kept the recovery key in my old windows and then I successfully encrypt all my data in hard. After that I went to my Drive C which I installed windows 7 and I saw that all my files became the green color(encrypt), and next I try to decrypt half of them not all.
When I change my windows to 7 again, I bop with this error <Access denied> or said with administrator permission you can open that file but actually I was admin.
And after that I cant open, decrypt, copy ,.... that green color files.
I tried with different way but unfortunately I saw this error again. Also I tried to encrypt my hard and then decrypt second time but it wasn't that solution, so I have two BitLocker Recovery Key.
If anyone know the right way or tell which option I can use in tutorial, please help me thx.

Hi,
Looks like you have made abig problem there i highly recomend that you reset your computer to its factory defaults.

Thx for answering my mail, how can I reset to default factory, you mean change my windows and if I reset, I will lose my data? pleeeease help me exactly I need my datas!!

Hi,
You need to refresh your PC