You probably can install it, but it's not going to run very well.
Your machine is underpowered. Despite Adobe's overly optimistic minimum requirements, the minimum RAM for Photoshop, as for the whole suite, is 8 GB.
Your display resolution is inadequate, some of the Dialog Boxes may extend below the bottom of the screen, etc.
Your video card really wants to have 1 GB of VRAM, you may be able to muddle through with your half Gig.
Where you're really going to be hurting is in scratch file space.
The rule of thumb I follow to figure out scratch space says to figure on 50 to 100 times the size of your largest file ever multiplied by the number of files you have open. I have seen the scratch file exceed 800 GB once, an admittedly rare occurrence, but it often exceeds 200 GB when stitching large panoramas and the like.
As an example—and stressing that I'm aware that others have even more scratch space than I do—I keep two dedicated, physically separate hard drives as my primary and secondary Photoshop scratch disks and a lot of GB free on my boot drive for the OS. I also have 16 GB of RAM installed.
Additionally, if you only have a single HD, i.e. your boot drive, you'd need it to be large enough to accommodate both the swap files of the OS as well as Photoshop's scratch.
Thanks for your advice.
I'm using cinema display and resolution is 1680 x 1050. VRAM is 256MB only and available space is 202.63GB.
If I can instal the software, I'll keep the file size under 50M.