An corrupted EFTFile1.sparseimage has appeared on my iMac but cannot deleted

Question

Hello guys! I need real hands-on practical help here, please.
I have already asked for help in here but didn't manage to get clear step by step help. Only got confusing redirection to other posts and very technical advice which really confuses me.
First of all, I have an iMac8,1 with Snow Leopard 10.6.7. Memory 2GB 800 MHz DDR2 SDRAM, and before the problem occured I had about 260-270 of free GB out of more than 300 GB.
I have discovered that my recycling bin contained a folder Recovered Files with a file EFTFile1.sparseimage. I only noticed it when I tried to Secure Empty the  Trash after running the tool Secure Delete Free Space from Internet Cleanup by SmithMicro (I don't know if this might be the cause of the problem).
When I got to deleting stuff from the Trush I noticed it was taking too long, so I decided to transfer the various files out of the trush and delete them individually. When I reached the EFTFile1.sparseimage I discovered this was about 261 GB in size - when I tried opening it, it said the following:
The following disk images couldn't be opened. Reason: corrupt image
After reading some online forums, I understand now that by deleting this sparseimage file I should be able to recover the free space. Some people suggested to use Terminal. Their instructions have been very confusing and also when I attempted once in Terminal, before submitting anything, a warning said I might loose important files. So, I stayed well away!!!
I want to stress, this EFTFile1.sparseimage isn't something I created (some forums have mentioned the possibility that some people may have done that for other purposes). The file appeared on my mac by itself. I guess, after using the SmithMicro free space delete?!
If anyone has the patience and knows of a real solution for this problem, I would greatly appreciate your help.
Cheers guys!

Answer 1

This is just a guess, but that file may be part of the mechanism that Internet Cleanup uses to erase the free space.  It might allocate a very large file, write erase patterns to that file, then (if allowed to complete), delete that file.  Since you didn't let it complete, that file remained.
To delete that file in a Terminal session, launch Terminal, then type this command, including a trailing space, without pressing the <return> key:
sudo rm -i
Then open the trash and drag that sparseimage file into the Terminal window.  You should now see the full path of that file following the space after the "-i" switch.  Now switch to the Terminal window and press <return>.  First you'll be prompted for your administrative password.  Type it and press <return>.  Next you'll be asked if you want to delete the sparseimage file.  Verify that it's the right file, then press <return>.  That should do it.
To terminal the Terminal session gracefully, type "exit" (without the quotes), press <return>, then quit Terminal.