DPI wont change

When I go to change my DPI settings it says, "Any font changes resulting from a new DPI setting will take effect after the fonts are installed and windows is restarted."

I click ok and then it says, "The required files are already installed on your hard disk. Setup can use these existing files, or Setup can recopy them from your original Windows CD-ROM or from a network share.

Would you like to skip file copying and use the existing files? (If you click No, you will be prompted to insert your Windows CD-ROM or to supply an alternate location where the needed files may be found)."

so then I click yes and it prompts me to restart my computer so I do it and then the DPI settings look the same as before but when I go into the menu it says they have changed.

How do I fix this? I can barely read the stuff on my screen so I kinda need it to be bigger.

Thanks