|"...unallocated space on C..."|
Unallocated space cannot be on C.
All drive letters assigned in the operating system are for logical (software) drives - the word logical is usually omitted - for hard drives they're assigned to one or more (NTFS, FAT32, or FAT) software partitions that have also been formatted on (a) physical hard drive(s).
The unallocated space may be on the same physical hard drive as the C partition, but when it's unallocated space it's not within a (NTFS, FAT32, or FAT) partition.
"In other (words) the (unallocated) space (and an existing partition) has to be right next to each other. You can not jump over one partition to add space to a different partition."
The unallocated space also must be on the same physical hard drive.
If both things apply, you can use either
- Vista's built in ability to expand a partition,,,,
The HELP documentation about how to use the built ability of Vista to expand - EXTEND - or contract - SHRINK - an existing partition without losing the data on the partition.
Control Panel - Classic View - Administrative Tools - Computer Management - Disk Management
RIGHT click on the drive letter of the existing partition, click on Help.
Manage Basic Volumes
Extend a Basic Volume
Shrink a Basic Volume
- OR - you can use a third party "partition manipulation" program to do that.
E.g. download and install the freeware Easeus Partition Master Home Edition.
"... it says the disk already reached the maximum number of partitions."
On one Physical hard drive, you can have up to four Primary partitions, or you can have up to three Primary partions and one Extended partition, and have as many Logical partitions in that Extended partition as you like, at least up to a point.
E.g. I have a 500 gb drive that has three Primary partitions , one Extended partition, the Extended partition has four Logical partitions within it - a total of seven partitions data can be stored on.