Best video program for upscaling video to 1440p

Ive had my 1440p monitor for a while. One thing thats annoying to me is watching various video formats that are in 1080p and seeing the nasty artifacts and blocks etc. that the windows media player does to bluray content or downloaded/converted mp4 mkv etc. Is there a better (preferably free) video viewer app that upscales or upconverts video content for full screen viewing that will work much better for me?

i have plenty of horsepower.... 2500k@4.8ghz and a 7950@1.15ghz.
 
I've honestly never used windows media player, I however have been using Media Player Classic for years and I've never needed anything else.

I watch 720p on a 1080p monitor and don't notice any artifacting or general oddities at all.
 
i do have media player classic for viewing flv and other files. i cant see much of a difference between regular and classic. to me it seems if all these hdtvs and home theater recievers have these fancy upscalers running off of very low compute and very low wattage cpu's... there should be a program out there for our uber fast computers that can upconvert and have beautiful results.