Hello gbalonek, welcome to Seven Forums!
I would suggest, after you have
copied out or made
back-ups of the data you need to save to external media, use Step One of this tutorial at the link below to do a wipe (
secure erase) to the entire Hard Disk Drive, running this "clean all" then using the outline in Step Two #2 to create/format and mark
Active a single 100GB partition using diskpart will get you the best possible space to do a
clean install of Windows 7 to; you can always
extend the Windows partition to include the remaining unallocated space on the HDD / SSD or
create additional partitions after the installation completes if you choose.
SSD / HDD : Optimize for Windows Reinstallation