If you installed Ubuntu "on top of itself", then you probably wiped out some files. To be sure, we will need more data.
First, if you have something really valuable on that disk, don't do anything else with i
t--everything you do decreases the probability of recovery.
If the data is really valuable, you may want to consider cloning the drive before doing anything else. Or, you may want to simply get it to a data recovery specialist.
To see what you actually have, please boot from the live CD (hoping you have this) and open a terminal and enter "fdisk -l" Post the results here.
If you do not have the live CD version, then you may be able to get into terminal mode by booting the install CD and entering ctrl-alt-F1 (or F2).
Some more on the nomenclature and mechanics:
- You do not have files "inside the kernel"---the kernel is one of many files that make up the OS. Data files are separate.
- When you install, the existing data on the disk is "erased"--meaning that it is unlinked. Some of it MAY still be there, depending on what gets written to the disk.
- As a practical matter--once you have re-installed--- there is no way to access the previous kernels, files, etc. (Unless of course, you had the data in a separate partition.)
Someone is going to mention "backup", so I'll not discuss that....