You must have ignored the warning message that you were converting to Dynamic disk which is meant for spanning large partitions across HD's.
To convert it back to Basic non-destructively use free Partition Wizard bootable CD, however this feature is only free in version 4.2 and prior. You can download the file here and burn to CD using Windows Image Burner or ImgBurn: pw422.zip ISO - Windows Live
Boot the CD, click on Disk # to highlight it, then from Disk tab select Convert to Basic Disk.
In order to do this you'll first need to delete the partition which caused the conversion.
Then post back a screenshot
of your maximized Disk Mgmt drive map so we can advise you the best way to convert a partition to Logical so that as many Logical sub-partitions can be added as needed. Often this is done with C if you have the 100mb System Reserved partition booting Win7..