There is a "cheat" to give you more space, NicoDe over at WoP postet how to do it:
1. Get the attachment from here:
http://forum.worldofplayers.de/forum/showpost.php?p=16153026&postcount=17 2. Edit the file&find: <max_weight mult="false" always_random="false" min="250" max="250"/>
3. Change min="" max="" to the value you like (both should be the same up to 10000)
4. Copy CookedPC folder into your Witcher2 installation (merge) and start game
All credits go to NicoDE at WoP one thing I might note:
If you gained the extra weight after the prologue it might be safer to set min="9900" max="9900" because 10000 seems the max value and there are items which also give small bonuses. Personally I set min="750" max="750" gaining +50 from prologue and +5 from gloves totaling 805. To uninstall just delete the abilities folder in CookedPC.