32-bit OS supports up to 4GB.
More specifically, there is a MEMORY MAP, and included in that memory map is:
a) Video memory
b) System memory
c) minor other stuff.
(There are some workarounds I believe, but that's beyond me)
If your VRAM is 1GB then Windows has to put that into the map, thus has 3GB left over. There's some minor other things which usually means you get 2.8GB approx usable.
2.25GB usable is an odd number, unless you have dedicated 1.5GB to video memory (either dedicated VRAM, or shared system). There are software issues that can reduce the amount usable, but 32-bit is still usually limited to 4GB total memory.
But...
I think you have some other issue, but it's not clear. Either way, maybe consider upgrading to Windows 10. You can then upgrade to a 64-bit version and utilize all of the system RAM and VRAM (sometimes VRAM is simply shared system ram).
You'd almost certainly need to do a CLEAN INSTALL. For example:
1) Backup all data needed, write down serials, programs to reinstall etc.
2) Create a W10 Install Disc that is 64-bit (HOME if you use HOME, and PRO if currently using PRO). That's from MS' Media Creation Tool:
https://www.microsoft.com/en-ca/software-download/windows10
3) Make a BACKUP IMAGE to be safe to a USB drive if possible (i.e. Acronis True Image or similar)
4) Boot to W10 install media, then DELETE all the partitions (optionally boot to a blank SSD if you want one)
*Using a spare or new drive is the safest, because you can insert the original drive if things don't work out.
5) do NOT insert a serial (will auto register one an internet connection is established)
6) Reinstall software, copy files etc.
*Then you should have access to all your system/video memory.