Just as an example, on my PC (Scan Priority set to Low) takes the scan 8-12 hours. This is because I have local backups of my C: drive (made with Windows 7 Backup) which the Scanner also scans. As I have around 5-10 backups (incremental) it basically scans 5-10 times my whole pc :S
On the other hand, our default client computer (which has no backup configured) with an SSD takes around 60 minutes for a full scan.
Time taken for the full scan is depends upon amount of DATA in your PC......
As mentioned, there are a bazillion factors that affect how long a scan takes. The speed of the computer, the speed of the drive(s), how many files to scan, what scan options are enabled, etc...
well thanks guys for your comments ... i guess its normal behaviour in that case