Are you trying to download and install it from the HP Support site? If not, the link to that site for the c4280 is: http://h10025.www1.hp.com/ewfrf/wc/softwareCategory?os=4062&lc=en&cc=us&dlc=en&sw_lang=&product=3192753
You will then have to specify whether you are using 32 or 64-bit Windows 7. If you don't know, the following gives information: http://windows.microsoft.com/en-US/windows7/find-out-32-or-64-bit
If that doesn't help, the HP Printer Install Wizard may help: http://h10025.www1.hp.com/ewfrf/wc/softwareDownloadIndex?softwareitem=oj-100441-1&cc=us&dlc=en&lc=en&os=4063&product=3192753&sw_lang=
If none of that helps, if you provide more information about what you mean when you say "I can not install ..." may make it possible for someone to provide additional assistance (e.g., error messages or other information about how you are trying to install and what happens).