7D records the video in 16:9 HiDef. Output in H264 codec. Window Movei Maker/DVD Maker seems to be able to open in Standard Definition (SD). Minimally, you need a paid software to open/edit it. Cheapest I am aware of is Sony Vegas Studio which you can buy at Challenger. Otherwise you could download a 30day trial and see whether it is suitable for your use.
With every conversion process, quality drops. Best is you convert it to MKV format for storage and then create a copy to edit it in Vegas and then render it into WMV format for PC or you could output to a DVD direct.