it's not such a good idea to delete them. the servicepackfiles folder is used by the SFC (system file checker) to prevent other applications from replacing system files installed by the service pack by invalid versions. it corresponds to the %systemroot\system32\dllcache folder. dllcache folder contains original files (from winxp cd and from automatic updates from winxp update MS website). servicepackfiles folder contains files from the service pack 1. which means if you delete this folder and some application replaces important system files, windows won't be able to replace them back, or it will use outdated versions from the winxp cd. meaning you save 200 mbs, but endanger you system.
I compressed the servicepackfiles folder. now it's just 170 mbs, not that much, and the advantage is that security is guaranteed, since SFC can still do its job