Sorry for the basic questions, but I need to know more about the symptoms.
What do you see happening on the screen when you boot? What stage does it get to before it goes blank? From your description, if you were able to go through the recovery disk process, your monitor is presumably working.
You can try creating a boot disk on your laptop (assuming you have a cd or dvd writer on the laptop), and booting the desktop from that. You will need to set the desktop to boot from removable disc rather than internal hard disk - to do that you need to enter bios settings (press F2 while booting) and change the boot sequence.
To create a boot disk on your laptop go to
and download, then copy to a CD. This CD is bootable and has a variety of diagnostic tools including virus scans. Put it in your desktop, after changing the boot sequence, and boot from that. You PC will then start up without using Windows and you can perform various diagnostics from there.
For more detailed instructions please post a reply here and I will try to help.