Which version of LW are you presently running?
I'd recommend XP btw, less problems to encounter.
1 (a) If using LW 4.16 or earlier, save the complete incomplete folder (back it up just in case to disk.) The download preferences are inside.
2 (a) If using LW 4.18 or the 5 beta, save both the incomplete folder & the preferences folder. The files inside the preferences folder called downloads.dat can be re-added to the new preferences folder after you install LW again.
In both cases, close LW after reinstalling the program in the new windows system. Then move the older incomplete folder across & replace the newer one. 2. (b) For LW 4.18 or 5.0 beta, move the downloads.dat file from inside the old preferences folder across to the new preferences folder & replace the one inside. These things MUST be done whilst LW is closed!