Typically, being stuck on "Welcome, Powering up" indicates a hard drive failure. For more resources and information on this problem see:
[http://www.fixmytivo.com/|TiVo Repair Guide]
Also, there are companies that can repair this problem. It'll cost you more if you send your TiVo off, but it might be worth considering. For example, see:
[http://www.weaknees.com/flat-fee-tivo-repair.php|TiVo repairs]
and also this place:
[http://www.dvrupgrade.com/dvr/stores/1/tivo-repair.cfm|DVRupgrade TiVo company]
If you want more self-help resources, see:
[http://www.weaknees.com/repair.php|TiVo troubleshooting]
Good luck!