Partitioning Error: Basic disk will be converted to dynamic disks

Hello cpsattawan. Welcome to the forum.

Don't convert the disk to Dynamic!

The are two drive file systems used for hard disks: legacy MBR (Master Boot Record) and the newer GPT (GUID Partition Table).

MBR disks can only have 4 Primary partitions. Any primary partitions added after 4 will require the the disk to be converted to a Dynamic Disk. Dynamic Disk is a supplemental system that lays over MBR. Windows can't boot from a Dynamic Disk. This system is used for data disks.

If you post a screenshot of your Disk Management window we can confirm this.

The easiest solution is to created an Extended Partition which will then contain Logical Disks. You can have many Logical Disks.
Partition / Extended : Logical Drives

Another solution is to delete one of the existing partitions. A common one to do this with is the Recovery Partition installed by computer manufacturers. What people do is burn the backup CDs of the Recovery Partition to keep on hand and then delete the partition, freeing a 4th Primary Partition for personal use.

A more complicated solution would be to convert the hard drive to GPT. But this process will delete all data on the disk so you need to be prepared with system Disk Images and personal data backups. You can practically have all the Primary Partitions you want on a GPT disk.

The solution is very simple. But before we venture into it, post a picture of your disk management so that we can give you best advice.

No need to delete any partition or to convert to GPT.