hardmodding a battery is not hard lol.. don't let people tell you what to do without researching it properly..... all you do is open the battery and break the 5th pin off.. i found a picture of exactly that...

bad thing is the battery is stuck on service mod... i have heard of people saying they turned them back from service mode but ive never gotten that to work....
here some easy instruction on how to hardmod a battery..
1)Take your knife/exact knife and CAREFULLY open your battery
2)once done, look for the connecter labled (ICO4 or CO4) (depending on your battery)
3)Next take your needle/safety pin and CAREFULLY remove the 5th pin (the pins start from the bottom left and up. So pin 5 should be the bottom one on the right.....depending on how you hold your battery.)
4)Put you battery back together (and if you want, glue it back on)

so buy another battery and hard mod it and just keep the battery put up for a rainy day.... glue it back together and you can still use it... just don't have the MS inserted.... but i would not use a slim battery.. get a cheap one from any retail store.. and make the Magic MS in XP and your good to go