Windows 7

I hope windows 7 will be much better than windows vista

Windows 7 is designed to search external hard drives, networked PCs, and libraries. Overwhelmed by your search results? You can instantly narrow them by date, file type, and other useful categories.

More details -http://www.microsoft.com/windows/windows-7/features/windows-search.aspx?tabid=2&catid=5

64-bit support
64-bit PC can handle larger amounts of information than a 32-bit system. Since it can use more RAM—4 GB and up—a 64-bit computer can be more responsive when you're running lots of programs at once.

Which should you buy? If you tend to have a lot of programs open simultaneously or need to switch frequently between programs—or if you just want to be sure your PC can take advantage of the larger amounts of memory available today—64-bit is a great choice. If you run only one or two programs at a time or have older hardware and software that isn't supported by a 64-bit PC, a 32-bit system is a good choice.

Whether you choose the 32-bit or the 64-bit system, Windows 7 is ready. To see if your PC is a 32- or 64-bit system