I have my desktop PC running Windows 7 and Acer netbook running Windows XP and I want to use its screen as second monitor for my desktop via LAN. Are there any software to do that?
Not sure if this is a exact dupe or not, so am going to answer...
MaxiVista is what you're looking for...cost $40 for a license, though.
OR, you could enable keyboard and mouse sharing between computers. Check out this webpage from Alternativeto.com...it lists the (mostly) free alternatives to Maxivista...as good of a list as you're gonna get...