Booting into XP or XP SP1 will usually corrupt the TiVo drive. I believe later version are ok.

Below I have shown how to find your source ID without TiVoWeb.

This is from my TiVo, after the mls / command look for the line with 'Setup', and make a note of it's FsId (mine is 2274)

Code:
[TiVo [p0] ~]# tivosh
% mls /
Directory of / starting at ''

    Name                      Type        FsId      Date  Time   Size
    ----                      ----        ----      ----  ----   ----
    AreaCode                  tyDir       2491  12/11/06 22:11     16
    Component                 tyDir          3  03/27/37 00:12     40
    DataSet                   tyDir       2508  12/11/06 22:27     64
    Database                  tyDir       1615  07/07/08 05:03    144
    Genre                     tyDir       1353  12/11/06 22:11   1920
    GuideIndexV2              tyDir       5886  07/08/08 17:12    372
    GuideIndexV2.temp         tyDir       2271  07/08/08 17:12      4
    Headend                   tyDir       2321  12/11/06 22:11    136
    HeadendPostalCode         tyDir       2322  12/11/06 22:11    224
    HeadendTms                tyDir       2323  12/11/06 22:11    180
    LogoGroup                 tyDir       6238  12/11/06 22:27     52
    MessageItem               tyDir       2302  12/11/06 21:38     48
    Person                    tyDir       6463  12/12/06 02:39     20
    PostalCode                tyDir       2489  12/11/06 22:11     16
    Preference                tyDir       6307  12/12/06 01:06     12
    Recording                 tyDir       1510  12/12/06 03:03    244
    Resource                  tyDir       1513  03/27/37 00:14     72
    Rubbish                   tyDir       2295  07/06/08 05:04    132
    Schedule                  tyDir       2275  07/08/08 05:03   1724
    SeasonPass                tyDir       5906  12/12/06 03:03     32
    Server                    tyDir          5  07/08/08 05:03    268
    Setup                     tyDb        2274  05/19/08 02:06   2924
    ShowcaseIndex             tyDir       6247  07/08/08 17:11    216
    ShowcaseIndex.temp        tyDir       5879  07/08/08 17:11      4
    State                     tyDir       2273  06/20/07 21:30    192
    SwModule                  tyDir       1549  03/27/37 00:16    112
    SwSystem                  tyDir       2270  04/14/05 13:38     40
    Theme                     tyDir       7279  03/21/08 17:18     48
    User                      tyDir       2293  04/14/05 13:39     16
    tmp                       tyDir       5243  07/08/08 20:59      4

%
Then type dumpobj with the number you found before (2274 in my case).
Code:
% dumpobj 2274
Setup 2274/10 {
  IndexPath      = /Setup
  Source         = 2274/12
  Version        = 83
}

%
The number next to Setup is your source ID (2274/10 for me).

Then follow the instuctions for loading the codes (note you don't need the tivosh step as you are already in there):

Code:
% source yourSTB.tcl
% yourSTB
% exit

[TiVo [p0] ~]# dbsetx yourSOURCEID CableBoxCodeNum 29992
[TiVo [p0] ~]# reboot
Peter.