Officially, Windows 7 Home version maxes out at 16GB. It is a limit that is added by Microsoft even though Windows 7 is capable of supporting much more.
The higher versions of Windows support more, but you'll have to buy the full version of the next better option, which is Ultimate or Professional to suit your needs.
Possible Solutions :
1. Upgrade to Windows 10, but I assume that if you haven't updated yet then you don't plan to update to Windows 10, which is totally understandable, which brings me to the next possible solution.
2. There is an unofficial patch that was available to download back in the time which enabled all the Ultimate Windows 7 features in any version of Windows 7. Not sure if doing so is ethical or not, I'll let you decide that for yourself, but those Windows 7 various versions limitations were kind of stupid anyway.
Note : This patch was meant mostly for personalization options. It might or might not do the job completely. Also, since it is unofficial, hence try at your own risk. Solution 1 is still the better way to go.
Anyway, the link to the patch is at : <link removed by moderator>