An example of an HDTV upconverter is the ADS HDUP-1500 HDTV UpConverter. A review in PC magazine gave the ADS unit a 2 out of 5. Here’s a quick run down on the ADS unit from their web site
If you’re looking for a box that offers video up-conversion to HD formats, consider products like HD scalers, video scalers and video processors, which provide video up-conversion (upscaling from standard definition to high definition) as one of their features. An example of a Video Scaler is the DVDO iScan VP50 High Definition Video Processor. The DVDO family of video processors sell from $1,700 to $3,000 SRP

“The DVDO® iScan™ VP50 is a high-definition video processor and A/V hub that converts standard definition, high definition (including 1080p) and PC signals from your DVD player, HD-DVD player, Blu-ray Disc player, HD DVR, game console or PC to any output resolution between VGA and 1080p, including popular HDTV resolutions such as 720p and 1080i.