Normally (if everything goes well) even lay persons can install most lx distros right out of the box without breaking a sweat. You may incur into some problems, even with the most recent distro, if your hardware is either brand new or its configuration very unusual. Barring that and assuming you are a newby to this world, your few next basic steps are:
1) get hold of the ISO image, "someone" used to do the install. Boot your machine from it (i.e. use it as a live OS)
2) To find out exactly what partitions were installed, run 'Gparted' form the live OS (it will allow you to do that if your ISO is for the Ubuntu distro). If you cannot find Gparted, I would recommend getting an ISO for a trusted and stable Linux version e.g. Ubuntu, Mint, CentOS, etc.) that includes Gparted and make a live CD from it by burning i and almost certainly for other flavors.) to and report here in the form:
/dev/-d-- [so many kB] [label or mount point] [file system format]
(I assume you are familiar with the partition scheme and naming for different type of volume; if not read about that, before you continue)
In doing so you will use Gparted to VISUALIZE only, not to re-partition or reformat anything, because that would probably wipe your win config clean. You don't want that.
3) All of the above is to determine whether you have a chance of recovering from what seems to be a failed install. If you see your partitions nice and clean, then we 'll look at your MBR and your GRUB and if they are corrupt, how to fix them.
NOTE: this is left to the appreciation of the moderators, but askubuntu.com may not be the best place for this. Other fora such as http://ubuntuforums.org will offer plenty of help at any needed level, be it for Ubuntu or when it comes to boot problem for a handful of other distros, that are either close or identical in terms of boot environment.
-ced
