Yes.
It depends on what aspects you are using. Elements on the cloud are ok, but the standard desktop applications of Microsoft Word, Microsoft Excel and Microsoft Outlook will not run if you download them onto a Windows XP machine.
It doesn't come with it, no. You have to buy Microsoft Office.
They both share Microsoft office and all the tools in Microsoft office (word, excel, PowerPoint etc).
No. Windows XP is an operating system. Microsoft Excel is an application. It must be purchased separately. When you buy a computer you could ask to buy a version of Microsoft Office and have it installed on your computer, but it does not come automatically with your computer.
Yes! Earlier editions may cause trouble, but Microsoft Student Encarta 2009 edition is running well on my Lenovo Core 2 Duo processor Windows 8 system. Even if it causes problem, try running in compatibility mode or upgrade your processor or memory or HDD.
Yes, Office Basic has Word, Excel and Outlook
No. Excel is part of Microsoft Office. Windows 7 is the operating system and it does not include the Office applications, which must be bought separately if you want Office on your computer.
Not even close. Microsoft Excel is a spreadsheet program. Windows XP is an operating system.
Using a Windows OS, Start->All Programs->Microsoft Office-> Powerpoint or Excel
The programs included with Microsoft Office Live are Microsoft Word, Microsoft Excel and Microsoft Powerpoint. The minimum system requirement for Windows to run these programs is Windows XP and for Mac it is Mac OS X 10.2.
Yes even though Windows 7 is newer.