Hex Workshop added additional support for large files and Unicode characters which broke compatibility with Windows 98 by requiring operating systems symbols and resources only available in Windows 2000+.
Hex Workshop v4 continues to operate properly under Windows 98.
You can increase the maximum text string placed on the Windows Clipboard by adding the following registry key:
HKEY_CURRENT_USER\Software\BreakPoint\Hex Workshop <version>\Advanced\MaxClipboardHexText to DWORD FFFFFFFF (or something greater then FF/256).
If you are running an application with Administrative rights under Microsoft Vista, drag and drop from the Windows explorer is disabled by Vista. This is true for all applications -- not only applications from BreakPoint Software.
You can turn off UAC, run explorer as Administrator, or run the application as a (non-administrative privileges) to work around this issue.