Most of the time viruses come from unknown emails, links in bogus web sites and from programs that are on your computer that are not used or have no updates available. Although there are other ways a virus can enter your computer these are the main reasons. You can avoid this issue by scanning emails attachments from your virus scanner if you have one, be careful of clicking on links in an unknown web site, remove all old programs from your computer and run all updates for your computer. This will eliminate getting a virus by up to 75-85% of the time.
A restore point is a windows function that you can use to back up your data and be able to go to that restore point when you have been infected with malware that you cannot get rid of. It can also be used to recover lost files and many other things. In short it is nice to have and is available on all windows platforms.
This is a mailware or virus type issue. It is attacking your windows logon script and in some cases can only be removed with a fresh install. This program attacks the userinit.exe file in your system folder. Although you can try to replace the userinit.exe file to gain a boot to the system you may not find the virus in question. I will not speculate on what causes the virus because I am not for sure. But I will say that I had a client contract the virus during a scheduled scan for his viruses. This is quite common in virus protection software that hasn't been updated with the new virus definitions. This is why it is important to run alll updates.
To find out the hardware PC information (i.e. memory, hard drive info, processor info, etc.) is to run an online porgram called Belarc Advisor. It is a free download and can give information about you PC that is very descriptive with all the information you need. This will allow you to tell your repair technician what he/she needs to know about your PC.