電腦中了木馬，HOSTS檔無法修改

請問版上的先進們，我的電腦hosts被竄改成
203.191.146.205 localhost
203.191.146.205 auto.search.msn.com
203.191.146.205 ok.mop-hz.com
203.191.146.205 about:blank
203.191.146.205 www.arswp.com
203.191.146.205 bbs.arswp.com
222.88.90.22 www.4199.com
222.88.90.22 4199.com
222.88.90.22 www.9505.com
222.88.90.22 9505.com
222.88.90.22 7939.com
222.88.90.22 www.7939.com
222.88.90.22 www.3448.com
222.88.90.22 3448.com
203.191.146.205 8925.com
203.191.146.205 www.8925.com
203.191.146.205 www.ttmp3.com
203.191.146.205 ttmp3.com
203.191.146.205 u1.sky99.cn
203.191.146.205 www.3tg.cn
203.191.146.205 toolsbar.kuaiso.com
203.191.146.205 www.kuaiso.com
203.191.146.205 kuaiso.com
203.191.146.205 www.copyso.com
203.191.146.205 union.copyso.com
203.191.146.205 ip.alexaanywhere.com
203.191.146.205 www.maohehe.com
203.191.146.205 www.365tan.com
203.191.146.205 www.winopen.cn
203.191.146.205 img.zhangxiu.com
203.191.146.205 www.tanip.com

既無法修改，也無法刪除，我有使用過安全衛士360進行掃描但是無效。。請問在不重新安裝windows xp的前提下，我該如何處理？