I have successfully upgaded my HP ThinClient T620's memory and hard drive, also installed Windows 7 64 Bit and Windows 10 64 Bit to it.
Here are some screenshots from Windows 10 installation. Memory upgrade to 8G, and hard drive changed to 120G. Default Spec:
- 1.5 GHz AMD GX-415A Quad-Core APU
- 4GB of 1600 MHz DDR3L SDRAM
- 8GB Flash Storage
- AMD Radeon HD 8330E Graphics (512MB min)