We have just migrated our systems from Windows to Ubuntu. We have more than 50 systems previously running Windows XP & Windows 7. After the release of 12.04 we decided to switch to Ubuntu. While we were installing Ubuntu 12.04 on Pentium 4 systems we have faced some issues.

We tried it with a USB flash driver & CD.

The typical configuration of the system is as follows:

• Pentium 4 with HT & 512 MB RAM,

• 40/80 GB IDE / SATA HDD.

In windows there were several partitions and data on all the drives in all the systems. We have addressed this by taking backup of the C: drive on other drives & while installing Ubuntu we have just deleted & the C drive & recreated Linux partitions as follows - /root , /Boot, /Home & Swap.(in 10 GB)

The problem is that the Linux gets installed without any error. However when I restart the system after the installation the system hangs in while detecting the HDD in BIOS and the system fails to start until I remove the HDD.

When I installed the previous Ubuntu version it worked fine, without any hassle. Also if we install Ubuntu 12.04 on same HDD on any other higher capacity system & reconnected to old system it works fine. How can I fix this problem?

Also, is there is any Antivirus which will give me real time protection on ubuntu 11 & higher versions with both 32 & 64 Bits?