Virus scan over network problems

Ok I have one machine on windows 7 x64 and one on Windows xp x86. Windows xp has its c drive shared to 7. I have now tried 2 virus scanners to do an in-depth scan of the shared c drive but in both instances they only bother to scan 300 files and then it just stops for no reason, is there any virus scanner that will scan the entire contents of the shared network drive. I have tried thus far eset and security essentials both behaved in the same manner and scanned hardly any files and just finished. Has anyone got any tips or maybe know why this is happening as i am a little stumped at the minute and can;t see why these scanners are behaving in this manner.