Partition on hard drive not seen by Windows

Hello everyone

This is my first post, so be kind.

I seem to have a problem and I hope someone can advise, (I am not experty really with computers.)

Anyway I am using a computer with several partitions. I tried resizing them with Partition Magic, and when the job was done, the app seemed to have done things I wasn't expecting, like swapping the names of the partitions around and stuff.

Then I realised that one of the partitions was no longer visible in 'My Computer'. At first I thought it was gone, then I noticed that the invisible partition still showed up in O&O Defrag window, but it was labeled 'unnamed'.

I tried renaming it (in Partition Magic) but it didn't help. Then I uninstalled Partition Magic in frustration. I thought I'd try another Partition software. Logical Partition (which is shareware) didn't seem to have the answer. When I try to reinstall Partition Magic, I get an error message telling me it won't install.

What can I do to make the invisible partition accessible in Windows again? Will I have to delete it?