"The 'Microsoft.Jet.OLEDB.4.0' provider is not registered on the local machine."

[DragonQ]

I haven't touched my program for about a month, suddenly, I go to add the completed Help File to the program (which works fine at my college), but then when I get home, the program won't start. The following lines:

frmData.Connection1.ConnectionString = "Jet OLEDB:Global Partial Bulk Ops=2;Jet OLEDB:Registry Path=;Jet OLEDB:Database Locking_
Mode=1;Data Source=" & Chr(34) & DBPath & Chr(34) & ";Jet OLEDB:Engine Type=5;Jet OLEDB:Global Bulk Transactions=1;Provider=" & Chr(34)_
& "Microsoft.Jet.OLEDB.4.0" & Chr(34) & ";Jet OLEDB:System database=;Jet OLEDB:SFP=False;persist security info=False;Extended_
Properties=;Mode=Share Deny None;Jet OLEDB:Create System Database=False;Jet OLEDB:Don't Copy Locale on Compact=False;Jet_
OLEDB:Compact Without Replica Repair=False;User ID=Admin;Jet OLEDB:Encrypt Database=False"
            frmData.Connection1.Open()

result in the following error:

{System.InvalidOperationException}
[System.InvalidOperationException]: {System.InvalidOperationException}
HelpLink: Nothing
InnerException: {System.Data.OleDb.OleDbException}
Message: "The 'Microsoft.Jet.OLEDB.4.0' provider is not registered on the local machine."
Source: "System.Data"
StackTrace: " at System.Data.OleDb.OleDbConnection.CreateProviderError(Int32 hr)
at System.Data.OleDb.OleDbConnection.CreateProvider(OleDbConnectionString constr)
at System.Data.OleDb.OleDbConnection.Open()
at Expenses_Program.frmMain.InitDatabase() in C:\Data\Adam\School Work\A2-Level\Computing\A2 Coursework\Expenses Program\frmMain.vb:line 198"
TargetSite: {System.Reflection.RuntimeMethodInfo}

I tried to reinstall Jet 4.0 SP8 - but it said I have a newer service pack than the one I was trying to install. Then I tried reinstalling Microsoft Office, which also did not help. Since I haven't touched my program except for this help file (which merely required the addition of the Microsoft Word 11.0 Object Library reference), I assume it's a problem with Office or Jet itself.

Anyone got any ideas as to how to fix this problem?