I would turn off all unnecessary startup items (windows 7-8 use the startup tab in MSConfig and turn off everything except your antivirus, Windows 10 use the startup tab on the task manager), clean your browser (cookies, cache, toolbars, and get an adblock), restart and try that. You could have large amounts of programs that are trying to do whatever in the background which will make everything on your computer slower. Also, check your disk space, if you have less than 10 gigs free on your primary drive, that can also slow down anything that uses a temp file (like your browser). After that, I would start uninstalling unnecessary programs and turning off auto-updates (which ping servers in your background). If all else fails, boot your computer into safe mode with networking and see if you're still slow, if you are, then I would do a clean copy of windows, if you're not, it's a program you're using.
NOTE: if your wife's computer is newer / more ram / better processor / better network card or some type of mixture of the four, comparing your connection to hers is like comparing your mustang's gas mileage with her hybrid... it's just not the same thing