First off, you can't simply put a hard drive from one computer to the next. Windows will BSOD because the hardware drivers are in conflict with those in Windows form the other laptop. The fact that it goes to Safe mode is, in itself, amazing. The other issue: Welded??????? You mead Soldered? I would plut in an external PS2 or USB mouse and see if that is recognized. Otherwise your handy work may have caused some damage to your Mobo on that laptop. You may ultimately need to attempt a windows reinstall on the laptop you "welded".
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.