Need help with error message from DTS

Running SQL server 2000 on SBS 2003 server fully patched.

I am using DTS to copy an Excel file to a SQL table.   Need help understanding the error message generated by DTS (see below)

My question:  See Message A below.
  Source:  'vol' (DBTYPE_WSTR)  (Column  in Excel file)
  Destination 'Volume' (DBTYPE_I8)   (Field in SQL table)

 What is a DBTYPE_WSTR ??  
 What is DBTYPE_I8 ?
What do these errors tell me about "general conversion failure"?

===================== Message A  =====================================
General conversion failure on column pair 1 (source column 'vol' (DBTYPE_WSTR), destination column 'Volume' (DBTYPE_I8)).)

I inserted the entire error message just in case you need it to answer this question:
==================  error message ==========================
Package Name: IN_LOAD_YYYYMMDD_xls_To_tblRawDataTempHoldString_Test
Package Description: (null)
Package ID: {63651FAD-1874-4523-A2FE-B691042C5E5A}
Package Version: {D9B5A65F-B6C8-4910-B2AE-B64759AE92AE}
Package Execution Lineage: {2B9986CD-657A-4718-8A95-BCF4A1054E11}
Executed On: SBS2003SERVER
Executed By: administrator
Execution Started: 10/27/2007 11:18:49 PM
Execution Completed: 10/27/2007 11:19:45 PM
Total Execution Time: 55.547 seconds

Package Steps execution information:


Step 'DTSStep_DTSDataPumpTask_1' failed

Step Error Source: Microsoft Data Transformation Services (DTS) Data Pump
Step Error Description:The number of failing rows exceeds the maximum specified. (Microsoft Data Transformation Services (DTS) Data Pump (8004202c): TransformCopy 'Set 1' conversion error:  General conversion failure on column pair 1 (source column 'vol' (DBTYPE_WSTR), destination column 'Volume' (DBTYPE_I8)).)
Step Error code: 8004206A
Step Error Help File:sqldts80.hlp
Step Error Help Context ID:0

Step Execution Started: 10/27/2007 11:18:49 PM
Step Execution Completed: 10/27/2007 11:19:45 PM
Total Step Execution Time: 55.531 seconds
Progress count in Step: 0Start Free Trial