Valve is the name of several artists.
1) Partnership from Finland.
2) Brazil rock band
1) a partnership of Sami Määttälä & Joni Autio, from Finland. Sami started his musical experiences sometime around 1996, with computer software called trackers. Joni has always been keen to different kinds of music. As he hasn't been producing as much as Sami, he has a sheer talent in writing lyrics. Valve was born in September 2006, when Sami had almost finished his new track, that didn't quite fit to be released under his other guises.
Sites: Discogs, MySpace and http://ValveMusic.net (official)
2) Valve consists of Vitoka (guitar), Rafael Ramos (guitar), Gabriel (bass), Lupercio (song) and Duduw (drums).
If you are scrobbling music from the various games by computer games company Valve Corporation, most likely the artist is actually Kelly Bailey, the company's in house composer. Please do yourself and Last.fm a favour and fix your tags.