You could RAID the two 160GB drives and have a fault tolerant storage area for 149GB I am guessing is what the 160GB's actually are. You could also short stroke one of them and use that short stroke partition for Virtual Memory space for Windows so that Windows isnt using the other drive in your system that may be fragmented for Paging. If you want to short stroke if you have say 4GB System RAM, then make a 8GB partition on the drive and point Windows to use this 8GB partition as the swap space for Virtual Memory, then make a partition for the rest of the space to store extra data there so if the 250GB drive is used which might be 237GB and you allocate 8GB to short stroking and then 229GB to extra storage space that can give you a performance benefit if your not running SSD's. If your running a SSD then the speed is all in the SSD.
I'd test the drives to make sure they are really healthy before using them as well to make sure your system wont BSOD on the short stroked virtual memory space due to a sick drive. Crystaldiskinfo can be used to look at the SMART data and see if they are flagged as troubled or not.
For short stroking the smaller the partition the better the performance however you want it to be 1.5x minimum of your RAM capacity and I'd suggest 2x your RAM capacity which will allow Windows to manage and expand and contract in swap space as needed without reaching a 1.5x ceiling.
For short stroking to work though the say 250GB drive needed to be removed of all partitions. Create that short stroke partition first as say 8GB if your have 4GB RAM and then create a partition after that for extra data storage. If you do it in reverse order then its not as good of performance because of where the data is on the platters is optimal at the start of the drive just past the MBR.
Before SSD's came along I use to short stroke for faster virtual memory performance. These days I have SSDs and so I havent short stroked in about 8 years.
https://lifehacker.com/how-to-short-stroke-your-hard-drive-for-optimal-speed-1598306074The best performance is the second hard drive being used primarily just as swap space for virtual memory. If you add data that is accessed on the larger partition on this second drive and make this drive then working as swap space for virtual memory as well as reading of data elsewhere on the drive then you take away from the performance gain optimization.