You can use the spell checker to verify English language spelling in records (Tools > Check Spelling or <F7>). See Check spelling in records for more information about how to check spelling in bibliographic records.
The spell checker skips (accepts as correct) diacritics and special characters in the ALA character set that the client supports.
The spell checker skips (accepts as correct) non-Latin script data.
Settings for the spell checker are stored in Options.xml, except for the user dictionary, which is a separate file (user.dic).
Both Options.xml and user.dic are stored in: X:\Documents and Settings\[user name]\Application Data\OCLC\Connex\Profiles\MyProfile\ (X = the letter of your hard drive).
To customize the way the spell checker works, see Customize the spell checker dictionary.