• Use the disk compression software supplied with DOS 6 or later. This has the disadvantages that the compressed drive cannot be usefully read from the RISCOS Desktop and that there is an increased risk of data loss if corruption occurs 
• Increase the partition size.
• If you have only one partition, simply create a further partition using !PCConfig

Unless you have space for both the old and the new partitions, you must back up all your data, delete the old partition, create the new one, and reinstall your data. 

However, if you have space for both partitions, then it is much easier and quicker to transfer the data using DOS. The details of this operation will vary according to whether you have one or two partitions, and their names, but here is the principle. You create the new larger, partition, copy all the data from the old partition to it, then make the PC card use the new partition. Once this is done you can delete the old partition. 

To create a new partition 

1. Use !PCConfig to create a new partition file of the required size as drive D, but call it NewDrv_C. If you have a second partition file already, make sure that the new one you are creating has a different name, otherwise you will overwrite your existing file.
2. Start up !PC. Your old file is drive C:, the new one drive D:
3. Use DOS’s XCOPY or Windows file manager to copy everything from drive C: to drive D:
4. Quit !PC.
5. Use !PCConfig to use NewDrv_C as drive C:, and not to use drive D:.
6. Run !PC. You should now have the new partition file as Drive C:, however it will not yet be bootable, so you must boot from a DOS floppy, run fdisk, and make the primary partition active.
7. Once you can boot from the new drive, delete the old Drive_C partition, and if you had an earlier second partition, drag it back to !PCConfig.

 
8. If you wish, rename NewDrv_C to Drive_C and update !PCConfig to reflect this change.