You can download a file explorer application from the Play Store and use it to move the files from the internal storage space to the SD card.
before you fiddle with it you may want to back up your photos on your PC. This is how to move them from phone to PC.
How to Transfer photos from HTC memory to PC
1) From the phone: select: Menu>settings>connect to pc>as disk
2) Attach phone to pc with usb cable
3) From pc open: Computer>removable disk F>dcim>100media
Note: you can also pull the mini sd card out of you phone and plug that directly into your computer. just make sure to unmount the disk through your settings options before you remove it from the phone.