You may not be doing anything wrong, we can't say by the limited information you
provided.  If it's a very large file and you don't have a fast connection, it could
take hours to download.

 If the download gets interrupted or stops for any reason, you should be able to
restart the download and it should pick up where it left off.  This can be a real
PITA and also wind up taking hours.

 Try contacting MS Support via Phone or email to see if they can help resolve the
issue, pending you don't have a slow connection.
Email and Phone support:
http://support.microsoft.com/oas/default.aspx?ln=en-us&c1=505&x=23&y=11&prid=101
82&gprid=422226

MS Office email support:
http://buy1.trymicrosoftoffice.com/buyus/contactus.aspx?culture=en-US

Sorry, I don't understand this at all.

1. You can't (legally) download any version of Windows XP, newer or
not. It's commercial software, for sale, and is not legally available
for download.

2. Do you perhaps mean that you are trying to download a Windows XP
*Service Pack*?

3. Whatever you are trying to download, what does it have to do with
"office home and student 2007"?

Answer the questions above, and also tell us what "I have been trying
for hours to get this download complete" means. What happens when you
try? If you get an error message, please quote it verbatim.

- From just WHERE are you trying to download a copy of Microsoft's
operating system?
- What is the URL for the download site?
- From WHERE did you buy the downloadable copy of Windows?
- Do you have an MSDN subscription?

It appears that the heading of your post has caused some confusion. Your
main body text refers to Office 2007 which 'isn't' windows xp it is
separate application that runs on windows xp. I gather you are having
problems but you don't give any details of what the problems are. The Office
application is quite large and, if you are using a slow connection, can take
many hours to download, especially when using Internet Explorer. Can we
first find out what the problems are and the we can probably advise better.
For example: Is the download not completing? Are you getting any error
messages? Are you actually using Internet Explorer to download? (Obviously
Internet Explorer doesn't have facilitates to continue a download if it is
interrupted in which case you would have to start all over again.) There are
freeware download managers that can help, but we can advise on those when we
have more information.

You seem to have made a mistake in your subject line in comparison to the body of your message.

You state, "download a newer version of windows xp" in your subject line.
Then you go and mention the, "office home and student 2007" in the message body.

Which is it?

I would guess at it being the latter for several reasons - but we won't go into those.

Going strictly by my assumption that your entire post is about obtaining a copy of Microsoft Office 2007 from the Internet legitimately - for example - from here:
http://www.windowsmarketplace.com/content.aspx?ctId=391&tabid=1&WT.mc_id=0207_09

More specifically in your case:
http://www.windowsmarketplace.com/details.aspx?view=info&itemid=3394360

Did you look through the online help and/or contact them?
http://digitallocker.windowsmarketplace.com/help.aspx

Beyond that - not knowing what type of internet connection you have - we are at a disadvantage.  It may be normal for a download this size fo you to take hours to get it.  It may not.  Help us help you by giving us as much information about your system and how it connects to the internet as plausible and relevant to this situation.

Also from:
http://www.windowsmarketplace.com/content.aspx?ctId=374&tabid=1

Scroll down to under the list heading "Downloading Software" and click on "I am
having problems downloading my purchase." to expand and view the proposed options.