add new partition after installation?

Yes.

You should be able to do that from Windows Disk Management.

You would shrink the 500 GB partition down to a smaller size, maybe 200.

That will leave the remainder of the drive as "unallocated space".

Then you would create a new partition from that unallocated space, also in Windows Disk Management.

There is some chance you will have to use another application to do the job, but usually it can be done from Disk Management.

kjo said:

windows 7 hp 64bit
500gb hdd

Windows installed on 500gb partition on hdd. Less than 50gb used.
Can I create a 300gb partition? Getting one 200gb and one 300gb. Thanks.

I've found, that readjusting partitions in so many different OS's over the years, it's been almost mandatory that I have a program on a bootable CD, that will do the job.

There are several Partition Manager programs, that will do the job, but not all are FREE. I like FREE!
So, I'm using a FREE copy of "EaseUS Partition Master".
I just boot up the PC with the programs boot disk and go ahead and shrink my C: drive leaving room for the new D: partition. Then I create and format the new partition. It only takes a few minutes and the process is completely safe.
I will NEVER set up a computer with only One partition on the hard drive. You need someplace for "Storage".

Good Luck,
TechnoMage