The common name for MicrosoftWindows.
Note: MicrosoftCorporation does NOT own this name! (Though various European courts have disagreed.) MicrosoftCorporation tried to sue Lindows.com (now Linspire) over dilution of their trademark, but judges in the US said that Windows was a common term used for any windowing system and there was plenty of prior art before they came along. However, as a result of the decisions of the European courts, Lindows was forced to change its name to Linspire.