asking for help

My operation system is windows xp sp2. and my anti-virus software is avast!4.8 Home Edition.
Sometimes after I scan my computer ,the Avast suggest me that it have found some virus but unable to delete or move to chest, more over, sometimes my avast can’t scan some of the compact packages,I am now asking for some solutin. Thank you. ???

For the files Avasts detects but is unable to move, please post the names and full paths of these detections.
Regarding the files unable to be scanned, this can be normal. Some files are zipped/encrypted or password protected by yourself, or more usually the program that created them, eg: AdAware definitions files. These are unlikely to contain malware.

Unfortunatelly, avast does not allow to move all the archive file (package) when a single file into it is infected. You have to manually delete the file and clean your Recycle bin.
For files in use, you can schedule a boot-time scanning:
Start avast! > Right click the skin > Schedule a boot-time scanning.
Select for scanning archives.
Boot.
If infected files are found, it’s safer to send them to Chest instead of deleting them.
This way you can further analysis them.