Ubuntu Linux, just like most Linux distributions, will happily co-exist on a hard disk with just about any version of Windows. This is a concept known as dual-booting. Essentially, when you power up your PC you will be presented with a menu which provides the option to boot either Ubuntu Linux or Windows. Obviously you can only run one operating system at a time, but it is worth noting that the files on the Windows partition of your disk drive will be available to you from Ubuntu Linux regardless of whether your windows partition was formatted using NTFS.
To day I have installed Latest Windows 7 and Latest Ubuntu 10.10 on my office system (Dual booting). This two operating system which I installed in HP dx 7200 micro towers.
Operating System: Windows 7 Ultimate 32-bit (6.1, Build 7201) (7201.winmain_win7ids.090601-1516)
Language: English (Regional Setting: English)
System Manufacturer: Hewlett-Packard