when i tried installing Ubuntu onto windows as a file..u know how it says you can install inside windows...well at the very end I get an error message...Why is that do I need to redownload the software?

What was the error message?

how did you kick off the install?
What did you download?

Do you mean Wubi? (https://wiki.ubuntu.com/WubiGuide)

If you use wubi from a Live USB, you may get an error message. There is a log file for the error. Check the log file, and post it here. Other users might be able to solve it.

My favorite way is

Place the ISO in the same folder where you have wubi.exe and then run Wubi.
For example, Wubi 11.10 requires the 11.10 Desktop ISO.

(If you just run wubi.exe without an ISO, it will download the ISO from the Internet. However, you can use it for one time only, so downloading the ISO file manually is better. You can burn a CD, create a Live USB or run it with wubi.exe.)

You can also run the wubi installer from a Desktop CD without any problems.

Review the log file as g00gle said. There is a bug 862003 which describes a case where wubi installs successfully but gives a permission denied error at the end.
Or it might be something different. There's no way to know without looking at the log file (you can find it in the %temp% directory called wubi-11.10-rev245.log). If you want to post it here, use http://pastebin.ubuntu.com/