OS file size and partitioning problem

I recently purchased a Dell PC with free Windows 7 upgrade. I only installed Mozilla Firefox and Norton Internet 2009 on the PC before I upgraded to Windows 7. I decided to do a custom install from the upgrade DVD so that I could change the partitioning following an article in the November issue of Australin Personal Computer Magazine.

The article said "Windows 7 requires around 10GB of hard drive space. We're planning to keep applications on the same partition as well, so we'll generously add another 20GB, making a 30GB partiition". So during the install process I deleted all the existing partitions, created my partitions with 30GB for the OS. The install process created the system section and everything worked as expected. To my surprise once the install had finished there was 27GB in the C:drive. I assumed it was keeping the old Vista somewhere.

I couldn't find a windows.old folder and in Disk Clean up the button 'Clean up System Files' didnt show for me - there is only one User account and I am the administrator so I didn't know what was causing that problem. So I decided to re-install Windows and increase the OS partition to 40GB - which I did. Only to find that this partitiion is now 35GB full. Again, no windows.old file can be found but the 'Clean up System Files' button appears - but there are no 'Previous Windows Installations' to delete. I decided to bear with it, but already I have a red warning light that the C: drive is nearing capacity.

So I decided to try a third install of Windows 7 and forget the idea of partitioning all together. But now I can only format the OS partition and can not format or delete any other partitions during the custom install process and all my old files were still there after the install. I have formatted the other partitions (i.e. not C:) now but still they can not be formatted or deleted in anyway through the install process. Windows 7 will not install on any partition other than C:. So it seems this 40GB is all I have for the OS, but it is now full.

Anyone have any ideas what I should do next. I have read everything I can on this site, but the solution seems to be always to delete partitions, which I am unable to do, and format partitions, which I have done (where possible).

If I could solve the problem as to why Windows is now 37GB would resolve my issue, but it is concerning that I can't change the partitioning also.

Did the Dell upgrade come with two disks?

At the very least you need at least a 50 GB partition for Widows 7

Yes it did come with two disks, but when I add the second disk it just says thanks for upgrading and takes me to the Dell website.

I have since found way to change the partitions so have increased C: to 140GB. I have a TB hard drive so it doesn't matter too much how much space the OS actually takes.

It is interesting what you say about the 50GB required partition size - I wish I knew that a few weeks ago. I forgot to mention I have windows ultimate too - so that might push the size up.

Thanks for your help.