Optimizing Removable Disk Drive Performance
Windows 98 gives you the option to use write-behind caching to improve the performance of removable disk drives, such as the Iomega ZIP or JAZ drive.
To set write-behind caching for removable disk drives:
1. Open System from Control Panel, select the Performance tab, select File System, and then select the Removable Disk tab
2. Select the Enable write-behind caching on all removable disk drives check box and click OK
If this causes a problem with disk operations, clear the Enable write-behind caching on all removable disk drives check box. 
Optimizing Removable Disk Drive Performance