Upgrading hdd to ssd

500gb alone is not enough for today games. For instance gta v 65gb.
Suggestions : os documents and games you want to start fast put on the ssd.
Use your old hdd as storage for long term or rarely played games

No problem!
To expand on the symbolic link thing I mentioned in case you or anyone seeing this would like to know, if you have your SSD as your primary (C) drive and your HDD as, for example, drive E (could be anything), then this is the general process for moving (an already installed) game to the HDD to save space on the SSD:

1) Open CMD and navigate to your steamapps\common folder
2) Create a folder on the secondary HDD for your steam games (e.g. E:\steamapps\common)

3) Without Steam running, move the game folder from your C drive to the E drive
4) Create a symbolic link between your C drive and your E drive
5) Launch Steam

Now, when Steam tries to load "C:\Program Files (x86)\Steam\steamapps\common\Counter-Strike Global Offensive" it will actually be loading the symbolically linked "E:\steamapps\common\Counter-Strike Global Offensive", the game data taking up space on the HDD at E:\ and not the SSD at C:\. In my experience, this works a lot better than trying to create a second library location from inside Steam (when I tried that, I ended up having to redownloaded 400GB because Steam refused to acknowledge the games at either location!)

To move the game back to the SSD from the HDD, close Steam, delete the symbolic link at C:\Program Files (x86)\Steam\Steamapps\common\ (it will have a little 'shortcut arrow' icon) and then move the game folder from E:\steamapps\common back to C:\Program Files (x86)\Steam\Steamapps\common

Oh good grief...you do NOT need that symlink stuff for Steam games. That functionality is built into the Steam client.

In the steam client:
Steam
Settings
Downloads
Steam Library Folders
Add library folder

You make an excellent point. Originally I used symbolic links, then started using this feature when I found out about it from a friend. Unfortunately, shortly after I set it up Steam updated and no longer recognised any of my appmanifest files. I could do absolutely nothing to get it to recognise my games' downloaded files, so I had to redownload the whole ~400GB. At the time, I was still on a 56KB/s connection so it stung a little.

I suppose if you make sure to backup the appmanifest files you might be fine, plus the Steam client may have fixed this issue in a more recent release (this was about half a year ago), but my very negative experience with this problem and the infamous Steam support team has kept me far away from using their library management system. Since I've gone back to symbolic links I've never had an issue. But hey, definitely worth checking out, I am quite biased about it all now. I just prefer the feeling of control with symbolic links. Appmanifest files have given me PTSD, so they can stay right where they are

USAFret points out that Steam has their own library management solution. Try using it since it is far easier than symbolic links. Personally I am avoiding it like the plague, but go ahead and trial it because it might not cause you any problems like it did me, and if it is fine then that's going to be the best option for you.

As I understand it, you intend to buy an SSD and perform a clean install of Windows (which is to say, starting from scratch with no programs or files)? The easiest way to go about doing this is by taking out the HDD and putting the SSD in its place. Then, install Windows however you would normally (via USB or CD or whatever). Once you have done that and Windows is working fine, plug in the HDD. Make sure your BIOS has the correct boot order, with the SSD as the first boot device (instructions vary depending on your motherboard, but it's usually F2 to get to the BIOS, then go to the 'boot' tab, then there is normally an option along the lines of "change boot order"). Save changes and reboot, then if all goes to plan the HDD will be present in the "My Computer" window.

At this point you can browse the HDD and copy off any data (like documents or pictures) you'd like to keep. Then, to erase the HDD, you can just right click the HDD in My Computer and press "Format". This will allow you to completely remove everything from the HDD. If you would like to partition the drive, Google "Create and Format Hard Disk Partitions" for some guides.

If you do all that, you'll end up with Windows on your SSD and a HDD that can be used just like a USB for anything large you don't want taking up space on your SSD. Many programs allow you to choose an install location, so you can indeed do it the easy way and install programs one by one. Just point them to the HDD instead of the SSD if you want to save space and you'll be fine.

Symbolic linking is only useful for programs that don't give you the option of being installed somewhere else, saving data somewhere else, or if, like I found (and again you might be like USAFRet and have no problems) with Steam, where they don't behave correctly in a non-standard location. With a 500GB SSD you'd be very unlikely to need to be that picky about what is installed where, so by all means disregard symbolic links.