There are two scenarios when it comes to win7.
One is that the win7 desktop offers the option to run programs in xp mode. However, it has been my experience that very few xp programs do run in this specialty mode from the win7 environment.
The second scenario is that win7 pro comes with Virtual PC, if im not mistaken.
Virtual PC is a specialty program that basically creates a bubble, ie a secondary environment, inside Win7. And from this bubble you can run a copy of the xp operating system. And from the copy of the xp operating system, you can run xp programs.
To describe it a bit differently, Virtual PC allows the XP operating system ( or linux or any other operating system) to be virtualized and executable, even though another operating system is running at the same time, eg Win7. So in affect Virtual PC allows a sub-operating system to run inside the main operating system.
To this end, once xp is installed in Virtual PC, then you can install programs in the virtualized version of xp. The virtualized XP will have its own start button, program files, desktop, shortcuts, etc... You can also run email and internet browsing from the virtualized xp.
So find the shortcut to run Virtual PC, if its installed on your Win7. After Virtual PC runs, see if it has XP installed in it. If it does, then run XP.
After the virtualized XP launches and the XP desktop appears inside the Virtual PC window, you can then install your xp programs in it and then run them from the virtualized version of xp.
When your done using XP, then close it via the Virtual PC main menu, eventhough you can also use the xp start button method too.
But there is an advantage with closing the virtual pc program instead of shutting down xp.
If you select the options to save xp's current configuration, then the next time you run xp it will as though it was coming out of hibernation. Also, if you don't save the configuration of xp after you install programs in it, then those programs won't be saved in xp.
Something to keep in mind, is that a virtualize xp cannot take complete control of you win7 system. for one thing, your computer hardware and its drivers are designed to run by Win7. So by virtue of the older / outdated xp o.s., it cannot take control of some of your computers hardware functions, like printing. Therefore, dont try to install hardware drivers in xp, because they simply won't work on your win7 machine.
Lastly, you will need to establish a folder for your personal files that will be shared by both Win7 and your Virtual XP. Then from Win7 you can access the shared folder and send documents to the printer that is controlled by WIn7.
Hope all of the above makes sense. It sounds real complicated at first. But eventually you'll see how really simple and logical all of the above is.
In any case, here is a search lookup with more info on Win7 Virtual PC:
http://www.bing.com/search?q=uisng%20virtual%20pc%20in%20win7%20pro&pc=conduit&ptag=ACE4F04C31DEE4BA4ABF&form=CONADR&conlogo=CT2786678&ShowAppsUI=1