HP Envy 5540 prints terrible

Generally, print quality problems ("stopped printing decently") indicates a problem with the print heads, as Canadian Tech said.  Before throwing the printer out, however, you should run a "print nozzle cleaning cycle," either by using the HP Toolbox (if you installed that software on your computer) or by using the printer's front panel controls.

See your User Guide (http://h10032.www1.hp.com/ctg/Manual/c04762607) starting on page 78.  The cleaning process is described at point 7 on page 81.  Although sometimes a second cleaning may be required, do not run the cleaning process more than twice.  All you'll do is use up ink (the cleaning process uses a lot of ink).

Printer performance has nothing to do with Windows 7.  It is the printer.  

Ever since HP stopped including the inkjets in the ink tanks a number of years ago, their ink jet printers now last about 3 years.  At about that age the inkjets, which are now part of the printer, will clog up and likely the only way to fix the problem is to replace the jets.  That part usually costs about as much as a new printer.  So, that means life-expectancy for those printers is only about 3 years.  Their warranty is only one year and repair cost by a pro will be much more than the cost of a new one.  Land-fill here we come.

HP makes a lot of pretty cheap ink-jet printers.  Often the cost of the new printer is less than the cost of replacing the ink tanks in your current one.

A much better alternative is the black/white laser printer.  NOT the colour lasers.  The B/W laser is a bit more expensive at first, but the cost of using it is less than half that of an inkjet.  And, it will last far longer.

Consider very seriously replacing with a B/W laser printer if you can live with out colour print.