There are several ways:
I did it last times with Partition Manager Free from Paragon; they also offer a version which runs from DVD / CD by its own without installing it to your system.
If you are using a tool like this, look for the capacity you have used on your partition / drive (assuming you are using only one partition (which is just one HDD letter in Windows), then you 'll need to start the laptop from CD, reduce the existing Windows partition (assuming you have only one partition!) so that you can create a second one with at least the capacity you need for your data. Format the new partition with NTFS and boot your system with Windows Recovery DVD (in Windows recovery mode from DVD). Enter command line and copy the contents of the first partition to the second one by using xcopy (I think Partition Manager is also able to do this job).
Afterwards you can start your system with Windows 7 installation, using the first partition as the installation / main partition. After installation has been finished, you can copy your data from the second partition to the first, erase the second partition and increase the first one again, if you like to.
p.s: there might be easier ways, but one would forgive me as I am a UNiX guy ... ;-)