You will lose these files if you format the drive which is what you will have to do to reinstall Windows 7.
You will have to either get a new drive and save these files to it (via USB hard drive enclosure or internal as long as you have a free drive bay and a data a power cable). Internal is better and faster of the two. Format to NTFS for compatibility for both.
You can use a Linux/Windows 7 disk to resize the partitions and leave free space at the end. Format the freed space as NTFS and save your files to it. Or install Ubuntu there. This all depends on just how much space is available though.
An internal or external drive transfer/backup of your files using the wubi install is really the simplest and safest option for you.
Maybe you know someone who has USB enclosure/extra drive you can borrow if you don't have one?
Have another computer with a big enough drive? Connect to network, make share and backup via wubi to it with SAMBA or someother means. RSYNC, GRSYNC (simple rsync gui), etc.
Note: If the drive Windows is on is modified then your ability to restore it might be broken if it uses a recovery partition for this. If you have a full retail install disk or something then modifying the disk should be ok.
Hints for better help:
Be more specific about the total size of your disk?
Free space available?
Useful tool:
http://partedmagic.com/doku.php?id=start
Maybe helpful:
Wubi/Ubuntu Running out of Disk Space
http://ubuntuforums.org/showthread.php?t=1577871
HOWTO: migrate wubi install to partition
http://ubuntuforums.org/showthread.php?t=1519354