You can happily be off-line, although you'll need to get Sandra on there somehow
.
I usually use Sandra's Burn-in (looping), 3dMark2001 (looping) and winamp (with a huge playlist). Leave them all running at once for a few hours and if it survives that,it should be fine! Plus it's still providing a little entertainment (music), and if the music stops you know it's probably crashed, so you don't have to keep an eye on it & can read a book or something.
Prime95 does put more stress on the CPU than sandra, so maybe run that too?
And I hope you're planning to OC that mobile... Seems a waste otherwise...
---
Epox 8RDA+ V1.1 w/ Custom NB HS
XP1700+ @200x10 (~2Ghz), 1.4 Vcore
2x256Mb Corsair PC3200LL/1x512Mb Corsair XMS PC4000 2.5-3-3-7
Sapphire 9800Pro (VGA Silencer Rev3) @418/742