First partition is 100MB and is described as the OEM partition,  This contains the boot files for Windows and will be created automatically for Windows regardless of the media (OEM vs Retail, etc.).  In a clean install, this can/should be deleted (although it will be created again as part of the install). second partition is 9.77GB and is described as Recovery partition,active primary partition,  This partition contains the factory image used to restore your computer to factory condition.  If you wish to do a clean install from disc (which I also prefer), then it can be deleted. third partition is 58.59GB, OS (C:) (Boot, Page File, Crash Dump, Primary Partition),  Obviously, this is your C: drive which holds your OS and programs (and probably your personal folders). fourth partition is 397.3GB (D:). This is often called a data partition ... it allows you to store data on one drive, so that if you ever need to reinstall the OS, then you can reinstall the OS to the C: partition and have all your data there waiting for you on the data partition, untouched. If you are doing a clean install and have nothing important installed on your D: drive, then you can simply delete all partitions and let Windows partition automatically (will create a 100MB System Reserved (same as the OEM partition) and the rest - 465GB - as the C: partition.  You can delete all partitions during the Windows 7 install ... when you boot to the Windows 7 DVD and it asks where you want to install to, select Disk Options and Delete the appropriate partitions (you do not need to create partitions, unless you want specific sizes, as they will be created automatically).
Hi I've many problems with my ~Inspiron 1546, running Windows 7 64 bit and have come to th conclusion that I need to reinstall the OS. I can't do a repair because my Installation disk doesn't have SP 1 whereas the OS on my Laptop does have SP 1. First of all my HDD appears to have 4 partitions but only 2 of them have drive letters.  First partition is 100MB and is described as the OEM partition, second partition is 9.77GB and is described as Recovery partition,active primary partition, third partition is 58.59GB, OS (C:) (Boot, Page File, Crash Dump, Primary Partition), fourth partition is 397.3GB (D:). I I have looked on line about installing/re-installng and have conflicting information.  One source said that I had to delete all partitions before installing Windows 7 and another that I should partition the disk before installing windows.  I'm not worried about having the recovery partition (if that is allowed) as I'm quite happy to use an installation disk. I don't understand the OEM partition, isn't it the same as C:? If I need to reformat and/or partition the diskhow do I go about it? Thanks
Windows 7 Re-Install