As for Windows NT, with the following exceptions:
Since Windows 98 does not implement much Unicode, Qt's Unicode support on Windows 98 is lacking. Note that Qt attempts to hide these differences - application programs can see that the fonts available are rather incomplete, but there is generally no need for programs to care. With other toolkits such as MFC, you often need to recompile. With Qt, your programs detect and use the capabilities of the Windows version they run on, that's all.
If you are experiencing a crash in comctl32.dll after debugging your Qt application then this is not a problem with Qt, see MSDN Knowledge Base article - Q255607 for more information.
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