Dual boot with windows 98 - Second Ubuntu installed accidentally – how can I delete the first one?

Sorry if the explanation below sounds confusing, I do have pictures that will make it more clear but I do not seem to find how to upload them.
Hello to all, I am back after a mini crash. A couple of nights ago I installed the program DeVeDe in my attempts to write a DVD from avi movies. Then I tried one avi and proceeded to make an iso image. It took for ever and decided to cancel the operation. I received a response if “I am sure...”, replied yes and all went fine and closed the computer. The next morning when I tried to reboot to Ubuntu it was impossible. I tried all combinations 15-generic. 16-generic and the corresponding recovery. I was always been sent to a Unix screen asking me to log in. I did log in and my data were accepted but it was impossibly to get to the graphic interface (my knowledge of Linux is very limited and for Unix it is zero).
I made the error to reinstall Ubuntu (feeling that it will overwrite and keep any thing I had previously installed) rather than delete. Then to make a long story short, I ended up with a new installation and I now I have 2 of each (15 and 16). The two old one's are listed as (on /dev/sda3) in the boot-up screen after the -generic. In addition I have 2 of each as (recovery mode) and 2 more as: Ubuntu, memtest86+
I now need to solve this problem before I go further, even if I have to repartition and reinstall Ubuntu, I am loosing much hardware space with the two systems installed and it is very confusing. Using gparted from within Ubuntu I found that I have the following partitions:
/dev/sda1 fat32 19.93 GB (my old partition for win98 OS and programs – C drive in win98)
/dev/sda3 ext3 10.25 GB (I suspect this is the old Ubuntu which I cannot start)
/dev/sda4 ext3 8.02 GB (I suspect that this is the new Ubuntu partition which is now operating – there is a / under the Mountpoint and the picture of a lock after the /dev/sda4
/dev/sda2 extended 19.47 GB (I am not sure what this partition is – I suspect this resides in my old drive D of win98 and includes the data of old drive D and the two linux-swap areas as shown below) – it has a lock next to /dev/sda2 and lba under flags
Under the /dev/sda2 the following (sub??)partitions are shown:
   /dev/sda7 Linux-swap 415.68 MB (has a lock next to /dev/sda7) and
   /dev/sda6 Linux-swap 878.49 MB (does not have a lock next to /dev/sda6) and
   /dev/sda5 fat32 18.20 GB (this is my extended partition in win 98 with all my files and data - D drive in win98)
I have gparted on a live CD and one thought I had is to delete partition /dev/sda3 and possibly sub partition /dev/sda6. Test if Ubuntu boots and then join /dev/sda4 with all the new space generated. If Ubuntu does not boot, delete all Linux and ext3 partitions, try to join all the left space in one and try to reinstall Ubuntu in that new partition. How well I will succeed I am not sure. Ideally if I can succeed to reboot Ubuntu after the first delete and enlarge the Ubuntu partition, it will solve most of my problems.
Any help will be greatly appreciated.
Thank you
Costas