Slow computer, possibly infected. Issues with Windows Updates.

Hi, can anyone help me sort my sisters old laptop- on which i'm running Vista Home Premium and i've been having a bunch of problems with, i've kind of been bumbling my way with things before I found the article on here about removing malware- originally I was getting a bsod 'irql not less or equal' 0x000000D1 (0x00000000, 0x00000002, 0x00000001, 0x8C7BB689) being caused by tcpip.sys (Address: 8C7BB689 base at 8C72A000, Datestamp 4b7d29d2) I think, I wrote this down although I don't have the original error logs (later I reset to factory settings) which I now seem to have resolved, the problem is I don't know what caused it and I don't have the old error logs.

I had problems installing windows updates where they either wouldn't download, (stuck at 0%) or would get stuck perpetually at the checking for updates phase and I ended up fixing this with ms fixit, then installed them- then after a while it kept finding large numbers of 'new' updates which I gather I already had, with dates from 2012/2013 etc. I'm still having this issue.

The problems reported by MS fixit (which still come up) are:

-Check for/ repair missing or corrupt files.
-Problems installing recent updates/ repair windows update.
-Service registration is missing or corrupt/ reset service registration
-Windows update error 0x80070057(2014-11-02-T-06_57_45P)/ Resetting windows update data store.

I also downloaded TDSS before the reset and it found the following:
Variant Win32/Somoto G (twice)
Win32\Somoto Q
Softpulse.B
Toolbar.Conduit.U

In the end like I said I decided to try reverting to factory settings to see if it helped, but I'm still having the same issues with windows update and things are still really slow, but no bsods.

Whats more before I reverted to factory settings Comodo was counting lots of outbound (?) network intrusions, that were coming from (Application) System. Source IP 192.168.1.248, to 129.168.1.255 and to . I don't understand this stuff, but I haven't had any more reported.

I've installed Comodo Internet Security since and run the antivirus, it found nothing. I tried to install Bitdefender and it's preliminary scan found nothing, although it won't run at startup and when I go and open it from it's directory its forever stuck on updating and tells me the service is unresponsive and a restart is required but this does not fix it. I'd try formatting and reinstalling windows but I can't find the install disc and other stuff that came with this laptop.

I've made a bit of a hash of things so far- i've been at this for a few days, i'd really appreciate it if someone could help set things straight for me. Thanks.